Seamless management of untrusted data using virtual machines

ABSTRACT

Approaches for managing potentially malicious files using one or more virtual machines. In response to receiving a request to perform an action on a file, a client applies a policy to determine whether the action is deemed trustworthy. The client identifies, without human intervention, a virtual machine, executing or to be executed on the client, in which the action is to be performed based on whether the action is deemed trustworthy. In this way, embodiments allow a user to make use of data deemed untrusted in certain cases without allowing the untrusted data from having unfettered access to the resources of the client. If the requested action is performed in a different virtual machine from which the action was requested, embodiments enable the performance of the action to be performed seamlessly to the user.

CLAIM OF PRIORITY

This application is a continuation-in-part of U.S. non-provisionalpatent application Ser. No. 13/115,354, filed May 25, 2011, having apriority date of May 28, 2010, entitled “Approaches for Securing anInternet Endpoint using Fine-Grained Operating System Virtualization,”the contents of which are hereby incorporated by reference for allpurposes as if fully set forth herein.

This application is related to U.S. non-provisional patent applicationSer. No. 13/223,091, filed Aug. 31, 2011, entitled “Approaches forAutomated Management of Virtual Machines for Running Untrusted CodeSafely,” the contents of which are hereby incorporated by reference forall purposes as if fully set forth herein.

FIELD OF THE INVENTION

Embodiments of the invention relate to the automated management ofuntrusted data using virtual machines.

BACKGROUND

Ensuring the security of Internet users and Internet connected devicesis one of the grand challenges facing us today. The current state ofaffairs is very problematic, as our cyber-security infrastructure iseasily and routinely subverted by cyber criminals, resulting in greateconomic loss. Every year brings deeper and more complex dependence bysociety on our cyber-infrastructure, and yet at the same time thecyber-security problem only worsens as the capabilities of thecyber-criminal mature. In effect, we are building mission-criticaldependence into virtually every aspect of human activities on acyber-infrastructure that is very insecure at its core.

The current state of our cyber-security infrastructure is due, at leastin part, to two fundamental limitations. The first limitation is afundamental mismatch between the design assumptions made by computersecurity programmers with how the vast majority of users interact withthe cyber-infrastructure (the “Security Model Complexity”) problem. Thesecond limitation is a lack of appropriate isolation of code and datafrom trusted and untrusted sources in modern computer systems (the “Lackof Isolation” problem). These two limitations of current systems aresomewhat orthogonal, but are both very important for securing a computersystem. The “Lack of Isolation” problem, in particular, is veryimportant because modern computer devices, such as a PC or cell phone,are typically general purpose devices that execute a vast wide ofsoftware from different sources.

The general purpose capability of modern computing systems isconstructed using a layered stack of hardware and software. An exampleof the layered arrangement of hardware and software that is present inmodern computer systems is shown in FIG. 1. At the lowest layer, thereis hardware with a small number of basic general purpose programmingcapabilities. Upon this hardware layer sits the firmware/BIOS which isresponsible for, among other things, initializing hardware resources andloading the operating system. The operating system (OS) provides a filesystem and functionality which may be used by a variety of differentapplications. On top of the OS layer run the various applications whichprovide user-visible rich functionality to the computer. Thefunctionality provided by the application layer is typically the primaryconcern of the computer user.

One advantage and consequence of the layered nature of modern computersystems is that the various layers may come from different vendors, aslong as the layers conform to the specifications governing the layerboundary (which may be based on open or proprietary industry standards).To illustrate an example, in a typical PC today the hardware may beconstructed around processor and chipset technology provided by Intel orAMD. The firmware/BIOS may be provided by companies like Insyde, AMI orPhoenix Technologies and may be written to conform to several industryspecifications such as UEFI and PI. The operating system (OS) mayoriginate from a company like Microsoft or Apple or may be a flavor ofthe Linux open source OS. Finally, the applications themselves areusually written to the specification of one of the operating systems andmay be provided by one of a large multitude of application vendors.

Note that some of the applications may themselves have a layeredarchitecture. A web browser, for example, typically includes a browsercore and may also download web applications in the form of HTML,JavaScript, and Flash programs from various Internet web sites. The webbrowser may run these downloaded web applications locally on top of thebrowser core. A typical web page contains HTML with embedded JavaScriptthat can change the HTML being rendered by the web browser dynamicallybased on user actions without having to re-download the web page fromthe web server. The HTML may also demarcate part of the web page to berendered by a plugin, which is typically a separate program that isinstalled on the computer. Plugins are often downloaded from differentsources over the World Wide Web. Thus, a modern computer runs code thatcomes from a variety of different sources. In particular, applicationprograms may originate from literally millions of different sources oncewe consider the collection of traditional local applications as well asweb applications that are downloaded from websites.

The integrity of a computer system when it runs application code fromdifferent sources (or even the same program being run by different usersof a shared computer) has traditionally been one of the responsibilitiesof the OS. The OS uses various hardware and software constructs likevirtual memory, processes, and file permissions to prevent code and databelonging to one program (or user) from affecting code and databelonging to another program (or user). This responsibility of the OS to“isolate” programs and data from one another often tends to compete withanother responsibility of the OS, which is to allow for co-operationbetween programs especially between user application programs and systemlevel services such as shared library modules, database services, andother higher-level common OS functionality. These two OS functions, toshare and to isolate, require the OS designer to make certain tradeoffson how much to share and how much to isolate.

As a result of these design tradeoffs, the resulting implementation ofmodern operating systems has grown to a complexity such that ensuringthe OS has no security issues is impractical. In mature operatingsystems, the security implementation is typically robust enough to workwell for normal programs under normal usage with no adverse impact onthe operation of the computer. However, most OS implementations are verylarge and complex bodies of computer code that may not possess asufficiently robust security system when interacting with programs thatare especially designed to take advantage of less-tested or unvalidatedcorner cases in the operation of the security subsystem.

These “security vulnerabilities” are not important for well-behavedprograms during typical operation, but are used extensively by cybercriminals to subvert the computer's security subsystems. Once thesystem's security is subverted, it is generally possible for cybercriminals to run any software under their control on the subvertedcomputer system.

The Lack of Isolation problem is made worse by the fact that a largeamount of code executed by computers today comes from sources outsidethe computer, some of which have explicit intentions of committingcriminal activities. This includes any program downloaded from theInternet or any web site visited by the computer. All downloadedprograms (good and bad) have the same OS and library services availableto them to use during their operation. Consequently, any program (evenmalware), can exploit any security vulnerability in the complex OS orweb browser environment and subvert the security subsystem that isolatesapplications from one another. For example, when a user visits a website, he or she is really running web application code developed by thepublisher of the web site. If this web site is malicious, then malwaremay be executed on the computer. Malware may be designed to exploit asecurity vulnerability in the web browser to take control of thecomputer system during subsequent web site visits, e.g., if you visityour bank's web site, your key strokes may be captured and yourlogin/password information for the bank may be transmitted to themalware publisher. Malicious programs may be designed for a variety ofpurposes, e.g., a malicious program may simply be designed to interferewith the normal operation of a computer rather than extracting usefuldata from the computer.

While some computer security professionals may understand the existenceof the Lack of Isolation problem, this problem is hard to solve in anypractical way because preventing applications from working orcommunicating with each other tends to conflict with achieving the goalof increasing seamless communication between different local and webapplications. There has been some work towards the isolation of web codefrom different sources being run by a web browser. Modern browsers haveattempted to create a level of sandboxing around downloaded webapplication code in order to isolate downloaded code from the rest ofthe computer and from each other. However, these models are fairlyprimitive in their ability to deal with the full gamut of securityissues that arise during the course of a typical user's web experience.For example, certain versions of Google's Chrome web browser'ssandboxing does not address safety issues arising from downloadedbrowser plugins and various types of native executables; thus, everycomputer system running certain versions of Chrome is vulnerable to azero day exploit attack against Adobe Flash or Microsoft Word as much asif the system was running a less secure or older browser with the sameAdobe Flash Plug-in or Microsoft Word plug-in.

Web browsers have been burdened with the need to ensure fullcompatibility to older and non-standard web pages in their efforts toprovide superior safety and privacy. For example, web browserprogrammers have had to make some relaxations in order to correctlyrender popular web sites that rely on the sharing of information betweenweb sites.

Last but not least, most web browsers vendors suffer from a hugeconflict of interest because their business relies upon monetizing theweb browsing habits of their users within their own business processesand with their industry partners. This monetization relies on data aboutusers' browsing habits which is contained in the web cookies that areset and later provided to web servers during the course of web sessions.Companies such as Google and Microsoft have a great interest in learningas much as possible about a person's browsing habits and typicallyarrange the default privacy settings of web browsers to be advantageousto them (but less than optimal from a security and privacy standpoint).This choice of default privacy and core functionality settings causesweb browsers to transfer large amounts of sensitive information from endusers' machines to Internet related businesses, such as Google,Microsoft, Apple, etc., thereby allowing such businesses to bettermonetize their customer base by offering appropriate products andservices and serving targeted ads. These same settings, however, can beleveraged by malicious parties to exploit security vulnerabilities.While all web browsers provide some level of control to thesophisticated user to tune his or her web browser functionality and/orprivacy/safety settings to browse more securely, the vast majority ofusers never change these default settings.

Some security researchers have also proposed the use of “clientvirtualization” (also called “Virtualization using a Hypervisor” in thedesktop) to solve the Lack of Isolation Problem. In one form of clientvirtualization, the user runs multiple independent operating systems ontheir laptop or desktop on multiple virtual machines (VMs) within theclient system which have been created using a hypervisor, such as fromVMware of Palo Alto, Calif. or Virtual PC, available from MicrosoftCorporation of Redmond, Wash. When client virtualization is used toachieve improved security, different VMs are used to run applicationsfrom different sources or of different types. For example, an OS in oneVM may be dedicated for accessing the corporate network that the usermay be part of and running corporate applications (local and web).Another OS in a second VM might be used by the user to run his or herpersonal programs and store personal documents. Finally, a different OSin a third VM may be used for general web browsing on the wider Internetand running native executables that may have been downloaded from theInternet. An example of such a solution is XenClient, which is made byCitrix Systems of Ft Lauderdale, Fla.

The use of classical client virtualization, as discussed above, to solvethe general code isolation problem in the context of Internet endpointssuffers from several drawbacks. A first drawback is that there is toomuch management overhead for the end-user. The end-user has the onus ofmaking the decision as to what VM to use for each activity. Any mistake,intentional or accidental, may subvert the integrity of the system.While many safeguards can be added as a layer on top of the corevirtualization technology to help prevent the user from making mistakes,this has not yet been demonstrated to work in a practical and robustfashion.

An additional drawback is that client virtualization, as describedabove, suffers from the problem that any VM that is used for general webbrowsing is just as vulnerable to a security problem as any monolithicsystem running a single VM while accessing web sites on the generalInternet. Therefore, it is quite likely that the VM dedicated to webbrowsing described in the arrangement above will be subverted by malwareeventually. Any subsequent activities in that VM, then, will becompromised.

Due to these reasons client virtualization has not been used widely toimprove the security of Internet endpoints.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are illustrated by way of example, and notby way of limitation, in the figures of the accompanying drawings and inwhich like reference numerals refer to similar elements and in which:

FIG. 1 is an illustration of the layered arrangement of hardware andsoftware present in modern computer systems;

FIG. 2 is an block diagram of the functional components of oneembodiment of the invention;

FIG. 3 is block diagram of the functional components involved inexposing a restricted copy of the file system to different UCVMs (andVVMs) according to an embodiment of the invention;

FIG. 4 is a flowchart illustrating the steps involved in a UCVMobtaining a copy of a new user file maintained in the file system storedelsewhere according to an embodiment of the invention;

FIG. 5 is an illustration of instantiating a plurality of differentvirtual machines using different templates according to an embodiment ofthe invention;

FIG. 6 is an illustration of a virtual disk based on VSS shadow copiesaccording to an embodiment of the invention;

FIG. 7 is an illustration of exemplary desktop of a client according toan embodiment of the invention;

FIG. 8 is an illustration of safely installing an untrusted applicationaccording to an embodiment of the invention;

FIG. 9 is a block diagram that illustrates a computer system upon whichan embodiment of the invention may be implemented; and

FIG. 10 is a flowchart illustrating the high level functional steps ofmanaging untrusted data according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Approaches for the automated management of virtual machines arepresented herein. In the following description, for the purposes ofexplanation, numerous specific details are set forth in order to providea thorough understanding of the embodiments of the invention describedherein. It will be apparent, however, that the embodiments of theinvention described herein may be practiced without these specificdetails. In other instances, well-known structures and devices are shownin block diagram form or discussed at a high level in order to avoidunnecessarily obscuring teachings of embodiments of the invention.

Functional Overview

Embodiments of the invention prevent malicious code, introduced into acomputer system, from compromising the resources of the computer systemthrough the use of dynamic operating system (OS) micro-virtualization. Acomputer system of an embodiment includes a number of independentvirtual machines (VMs) that each executes a full operating system (OS).A block diagram of client 200 according to one embodiment of theinvention is shown in FIG. 2. The term “client,” as broadly used herein,represents any type of Internet endpoint or computer system capable ofconnecting to a network and executing a virtual machine. Non-limiting,illustrative examples of client 200 include a PC, a laptop computer, atablet computer, a cell phone, a personal digital assistant (PDA), andthe like.

In an embodiment, client 200 may correspond to a server. Thus, while useof the term “client” in other contexts might exclude an interpretationthat includes a server, as broadly used herein, client 200 may beembodied on a wide variety of machines, one example of such being aserver. Thus, as the Applicant may be his or her own lexicographer, asused herein, the term client 200 expressly includes a server. Forexample, non-limiting, illustrative examples of client 200 include a webserver, an application server, a file server, a RPD/x-Windows/SSHserver, and a cloud server. Indeed, implementing embodiments of theinvention upon a server may yield many benefits. Themicro-virtualization techniques employed by embodiments provide anefficient mechanism for eliminating the risk of executing untrusted codeand/or interpreting untrusted data in accordance with different policiesto manage such risk. As such, a device, such as a server, whichinteracts with (a) numerous sources of untrusted code and/or data and/or(b) two or more corporate entities having different policies towardsmanaging the risk of untrusted code and/or data, may benefit fromembodiments of the invention.

Client 200 includes a number of virtual machines (such as 230, 240, 250,and 260, for example) that execute on hardware 210 of client 200. Thevarious VMs within client 200 may be used for separately executingprocesses associated with different activities. One such VM, namely“VM0” (i.e., VM0 230 of FIG. 2), is secured so that VM0 may serve as theroot of trust with a guaranteed integrity. VM0 may contain coreoperating system 232 and one or more applications 234. In the embodimentshown in FIG. 2, VM0 is not accessible over any network, such as theInternet. As shall be explained below, VM0 provides a secure environmentin which operating system 232 and one or more applications 234 mayexecute without risk of exposure to malicious code.

Other VMs, such as VMs 260, 262, 264, and 266 in FIG. 2, may be created,maintained, and destroyed on-demand using a very efficientmicro-virtualizing hypervisor 220. Using efficient micro-virtualizationtechniques, the latency of starting and stopping activities orapplications which run in their own VM in embodiments is very low,thereby providing a practical user experience while employing full OSvirtualization.

Embodiments address and overcome many disadvantages, such as the Lack ofIsolation Problem, experienced by modern general purpose computersystems that execute code from different sources and of differing trustlevels; nevertheless, embodiments maintain compatibility with currenttypical real-world usage of computer systems by corporate andnon-corporate users. This is so because any activity which is notpreviously deemed trustworthy is performed in a separate VM by certainembodiments, and so all code which may be potentially malicious isexecuted in its own VM that is destroyed after its immediate use isended, thereby preventing any malicious code from effecting any lastingchange to a computer system according to an embodiment of the invention.

The Trusted Virtual Machine—VM0

In an embodiment of the invention, a special virtual machine, referredto herein as “VM0,” is created to be a trusted and secure portion of acomputer system. FIG. 2 depicts VM0 230 according to an embodiment. Toachieve the property of being trusted and secure, VM0 230 may bepermanently disconnected from any network (i.e., VM0 230 is notconnected to any local network or the Internet). Specifically, VM0 230may not contain any type of networking stack, such as a TCP/IP networkstack, and may not possess or have access to any networking hardwarethat could allow for communication between VM0 230 or any applications234 executed thereby and the Internet. Thus, the only way to installsoftware onto VM0 230 may be to have physical custody of client 200 andmanually install the software on VM0 230. Note that a client may containany number of VM0 virtual machines. While FIG. 2 depicts an embodimentcomprising a single VM0, other embodiments may comprise two or moreVM0s.

In certain embodiments, one or more applications 234 executing withinVM0 230 do not have any access to a network, must be fully selfcontained in their functionality, and must rely only on local code anddata for all their functionality. All applications that need to accessthe network will therefore need to run in a separate virtual machineoutside of VM0 230, as shall be described in further detail below. It isenvisioned that the software (such as one or more applications 234)running in VM0 230 be selected at the time client 200 is manufactured orfirst configured for use in a controlled environment. Because VM0 230 isnever connected to any type of network, such as a TCP/IP network, allcommon types of network initiated attacks cannot be waged against VM0230, thereby rendering VM0 230 immune to such attacks and safe ascompared to any computer or VM that is connected to the Internet. Also,in an embodiment, VM0 230 may execute a different type of operatingsystem than used by UCVMs (discussed below) in client 200. In this way,VM0 230 would be immune or resistant from attacks that typically affectthe guest operating systems running in the UCVMs of client 200.

In an embodiment where hypervisor 220 is a Type 2 hypervisor, whenclient 200 is booted, only VM0 230 is started by the BIOS or firmware ofclient 200. Once VM0 230 is running, VM0 230 can start hypervisor 220immediately or on demand. In another embodiment, where hypervisor 220 isa Type 1 hypervisor, hypervisor 220 is first started by the BIOS whenclient 200 is booted and VM0 230 is launched by the hypervisor 220.Hypervisor 220 is a software component that is responsible for creatingother VMs which each execute independent instances of the operatingsystem. These additional VMs are instantiated by VM0 230 and/orhypervisor 220 to run any untrusted code or code that needs to accessthe network. Untrusted code in this context is any code which has notbeen pre-approved as being trusted by an IT administrator of client 200.The additional VMs are started “silently” and automatically by client200, e.g., these VMs are started transparently to the user and withoutthe user having to do anything explicit (note that a user may stillmanually initiate the creation of a VM in certain embodiments). Theseadditional VMs are also not explicitly visible to the user; instead, allthe user sees on the desktop is familiar objects (such as icons,windows, and applications) without any indication that multiple VMs areexecuting in client 200. Embodiments of the invention follow rules thatgovern what application activities are assigned to which particular VM.These rules are described below in greater detail.

In another embodiment (not depicted in FIG. 2), VM0 230 may have anetworking stack that is firewalled off from the network usingwell-tested firewall software, thereby allowing VM0 230 to have accessto a computer network. Such an embodiment may only allow connectionswith a specific Internet system so that the software inside VM0 230 maybe updated from a designated update server. For example, the firewallsoftware may only allow VM0 230 to connect to one or more serversassociated with the IT administrator of client 200 and may prevent VM0230 from establishing a connection with any other endpoint on anynetwork.

In an embodiment, VM0 230 may communicate with other components ofclient 200 using secure channels. For example, VM0 230 may communicatewith other entities in client 200 using a shared memory channel mediatedby a hypervisor. Thus, VM0 230 is not isolated from the remainder ofclient 200, but nevertheless, processes and data within VM0 230 areresistant from external attacks.

Interaction with an User Interface

All code responsible for generating a user interface (UI) not associatedwith an application may be maintained in VM0 230. Consequently, all UIinteraction activity with the desktop between a user and softwareexecuting on client 200 may take place between the user and VM0 230,which maintains a unified desktop for all applications running in allVMs. Interaction between the user and applications running in VMs otherthan VM0 230 takes place indirectly via VM0 230. For example, when theuser enters a password for a web site whose browser and HTML/Javascriptcode is running in an untrusted VM, the password is first directlyprovided to VM0 230, which then transfers the information to theuntrusted VM. Furthermore, the untrusted VM's display is rendered on toa virtualized display, which is then composed into the VM0 230 desktop(as appropriate) by controlling code running in VM0 230. As codeexecuting in VM0 230 is trusted, the user may trust any user interfacecontrols displayed on a screen since all code responsible for renderingthe user interface is trusted.

This approach is quite different from prior systems where often the codethat controls the full desktop experience is untrusted. Consequently, ifthe code responsible for generating the user interface is corrupted bymalware, then the user interface may be used as a tool to deceive theuser. For example, malware may cause a user interface control to bedisplayed that requests the user to submit an authentication credentialwhich will be used for improper purposes by the malware. However, thisproblem is overcome by embodiments of the invention—since all coderesponsible for rendering user interface controls executes in VM0 in anembodiment, malware is prevented from hijacking or corruptingUI-rendering code.

To illustrate an embodiment of the invention, consider FIG. 7, which isan illustration of exemplary desktop of client 200 according to anembodiment. As shown in FIG. 7, process 704 is responsible for renderingdesktop 706 on a physical display of client 200. Process 714A runs inuntrusted VM 714 and does not have complete access to the file system ofclient 200. When any process inside VM 714 requests access to the filesystem of client 200, it is intercepted and process 702 is responsiblefor rendering a window 708 depicting the contents of the file system ofclient 200. Process 702 has the option of selectively displaying whichcontents are available to the VM 714 based on policies as set forth bythe IT administrator or the user. VM 710 in FIG. 7 that runs thesolitaire game is implemented such that the display of VM 710 is avirtualized display, which is then composed into the desktop 706 (asappropriate) by controlling process 704 running in VM0 230. The displaysof VMs 712 and 714 are rendered on the desktop 706 in a similar fashion.

The Legacy Virtual Machine—LVM

FIG. 2 depicts a legacy virtual machine (LVM) 240 according to anembodiment of the invention. LVM 240 may contain operating system 244.LVM 240 serves as the primary entity being managed by the ITadministrator of client 200. As such, LVM 240 provides an environmentthat is analogous to the managed enterprise OS of corporate computersystem in that an IT department may install and maintain variousenterprise applications within operating system 244 of LVM 240. In anembodiment, operating system 244 of LVM 240 may correspond to aMicrosoft Windows OS or any other general purpose OS such as Linux orMacOS.

In an embodiment, LVM 240 is responsible for storing the main filesystem 242 of client 200. File system 242 may contain the user's profilefolder containing the user's settings and files.

LVM 240 typically only runs infrastructure OS programs and programs thatare used for the purpose of managing client 200 and trusted enterpriseapplications. Other user programs (especially those that involveexternal components or consume untrusted data) do not run in LVM 240,but instead, run elsewhere in separate VMs (such as a UCVM as describedin more detail below).

In an embodiment, the network access of LVM 240 is restricted to justthe corporate network as implemented by firewall VM 250. Firewall VM 250is a specialized virtual machine that comprises firewallsoftware/applications to restrict network access of VMs running inclient 200 to appropriate and/or necessary network access points. Suchpractice is consistent with the need for only the responsible ITadministrator to be capable of connecting to LVM 240 to manage LVM 240and processes executing therein.

In one embodiment, LVM 240 and VM0 230 may be implemented in a singlevirtual machine.

Untrusted Code Virtual Machine—UCVM

When a user wishes to run any application that requires access to eithera network or untrusted data (untrusted data is any data that originatesfrom outside client 200), the application is run inside a dedicated VMthat is created on-demand by hypervisor 220. This dedicated VM is calledan Untrusted Code Virtual Machine (or UCVM). FIG. 2 depicts severalUCVMs, namely UCVM 260, 262, 264, and 266. A UCVM operates under theassumption that, in general, any code that connects to the network andinteracts with arbitrary code executing on an external device may atsome point be compromised. This assumption also applies to trustedapplications that interact with data originating from outside thecomputer system executing the trusted application, because such datamay, at some point, contain embedded malicious code. To address suchpossibilities, such applications are executed in a UCVM to prevent anymalicious code, inadvertently introduced into the UCVM, from having thecapacity to affect any change outside of the UCVM.

In an embodiment, a UCVM is created by (a) cloning a copy of LVM 240, ora stripped-down version of LVM 240, in memory and (b) providing accessto a restricted file system to the newly created UCVM. For example, UCVM260 comprises restricted file system 260A, UCVM 262 comprises restrictedfile system 262A, and UCVM 264 comprises restricted file system 264A.Each UCVM possesses its own instance or copy of the operating system,which is isolated and separate from the main operating system (includingits code and data) executing within VM0 230 or LVM 240. For example,UCVM 260 comprises operating system 260B, UCVM 262 comprises operatingsystem 262B, and UCVM 264 comprises operating system 264B.

To provide a low latency user experience, UCVMs may not be booted fromscratch each time an application is needed to be started. Instead, aUCVM may be created very quickly by cloning the UCVM from a template VM(with a booted OS) that has been pre-loaded in memory at system boottime. In an embodiment, the template used to clone a UCVM may beselected from templates 238 stored in VM0 230. A variety of techniquescan be employed to make this cloning operation as fast as a few 100milliseconds. Multiple types of templates may be used by a system tocreate UCVMs depending the nature and type of application(s) to be runinside the UCVM, as discussed in greater detail below in the sectionentitled “Cloning a UCVM from a Template.”

Cognitive assist module 236 is software that is responsible forimplementing the rules and policies of embodiments as well as helpingthe user of client 200 in understanding and navigating the securitymodel employed by client 200 on an as-needed basis. Cognitive assistmodule 236 helps decide what activities run in which UCVMs, includingwhen VMs are created or destroyed, and what kind of access to networkand file system resources each UCVM has. Cognitive assist module 236also helps protect the user, e.g., when a user is fooled by malwarerunning in a UCVM and is in the process of providing some informationthat they have previously provided to enterprise code running in LVM 240(for example a password), then cognitive assist module 236 may detectthis situation and prevent the user from providing the information(which may be secret corporate information) to the malware.

Regarding the restricted file system of each UCVM, each UCVM has accessto a private copy of a subset of the files in file system 242 on client200. A UCVM may only have access to those files which the UCVM shouldneed for the correct operation of the application executing therein. Forexample, user files are usually not required for correct operation of anapplication executing in a UCVM and thus are not typically exposed to aUCVM. On the other hand, if a UCVM is created as a result of the userwishing to edit a document using an application, such as MS Word, then acopy of the document the user wishes to edit will be provided to therestricted file system of the UCVM at the time the UCVM is created.Advantageously, using UCVM 260 as an example, if a process executingwithin UCVM 260 makes any changes to any files in restricted file system260A, then these changes do not impact the files stored in file system242 maintained in LVM 240 because such changes are only made torestricted file system 260A maintained in the UCVM and are notpropagated, without express consent from the user, to file system 242maintained by LVM 240.

In a typical use case of a UCVM, the UCVM may run a local application oran individual web page session. When a user is done running the localapplication or navigates away from a web page to another page with adifferent Internet URL domain, the corresponding UCVM is destroyed. Anynew local application or web application will be run inside a brand new,separate UCVM that is cloned again from a clean UCVM master template.Thus, if there has been any compromise to the UCVM during the course ofrunning some malicious code that was introduced into the UCVM, then theadverse affects of the security breach are isolated to only the affectedUCVM and are lost when the UCVM is destroyed.

For example, assume that a user double-clicks on a MS Word document iconin Windows Explorer. Embodiments create a special UCVM to run the MSWord process. In a particular embodiment, cognitive assist module 236 ofVM0 230 may dynamically create the UCVM using a template in one or moretemplates 238 or use a pre-existing template in memory or on the disk.The template selected by cognitive assist module 236 may be selectedbased on what activity is to occur within the UCVM, i.e., the selectedmay be designed to create a UCVM having characteristics that are optimalfor running a text editor therein. The created UCVM contains a copy ofthe operating system as well as a restricted (local) copy of the filesystem. This local copy of the file system in the UCVM contains all theusual Windows and Program files; however, the user's profile folder inthe local copy of the file system contains only the single target MSWord document being opened.

As another example, assume that three tabs are open in a web browser andfurther assume that each tab is open at a different web page. Inconsideration of the code which may be contained or embedded on a webpage, each web page may be properly considered a web application. Inembodiments of the invention, the code responsible for rendering theuser interface (UI) of the web browser runs in VM0 230. On the otherhand, executable code for the three web applications runs in threeseparate UCVMs. A core HTML/Javascript engine runs in each of the threeUCVMs. A copy of the file system within each of the three separate UCVMsdoes not contain any part of the user's files, as they are not requiredfor the task performed by each UCVM, namely displaying a web page. Thus,each web application (or web page in this example) is completelyisolated from the rest of the system.

In an embodiment, a UCVM may be connected to the Internet according toan access policy determined by the nature of the code running within theUCVM. To illustrate, web pages are typically restricted as per a strict“same origin policy” similar to the rules implemented by modern webbrowsers. In the “same origin policy,” scripts running on web pages arepermitted to access methods and properties of other scripts originatingfrom the same site with no specific restrictions, but are prevented fromaccessing most methods and properties across web pages on differentsites. Untrusted native applications running outside of the web browserare restricted by default to be able to connect only to the domain fromwhich the program was downloaded (and to specific content deliverynetworks (CDNs) that may be in use by the domain in question).

This level of network access for downloaded applications can beexplicitly changed (increased or decreased) by the end-user to includeadditional sites on the Internet. End-user control over what a UCVM canconnect to may be subject to certain limitations related to corporatenetworks and sensitive web sites (such as a bank and web mail provider).For example, any code running in a UCVM may not, in general, access anysite on a corporate Intranet to which client 200 is connected.Applications that need to connect to the corporate Intranet may need tobe signed by the IT administrator of the domain. Similarly, non-webuntrusted application code in a general UCVM may not connect to a website associated with a search engine or bank or other sites that mayhave been previously identified as being “off limits.” These connectionscan only be made through a web browser (which spawns UCVMs bound tothese special domains) or from a special purpose LVM called a VVM, whichdescribed in further detail below.

In an embodiment, there is no communication channel available for anapplication running in one UCVM to communicate with an applicationrunning in another UCVM. Thus, applications running in UCVMs arecompletely isolated from each other and from the other applications inthe system. This is well suited for running downloaded third party localapplications which are generally designed to be self-contained or forInternet applications (web pages are not supposed to rely on anycommunication between applications within the web browser). In analternate embodiment, communication between an identified set of virtualmachines can be enabled by a person with sufficient privileges, such asan IT administrator for client 200.

Firewall Virtual Machine

In an embodiment, the implementation of the network access restrictionsis done in a dedicated VM called a firewall VM. FIG. 2 depicts anexemplary firewall VM 250 of an embodiment. Firewall VM 250 runs anisolated operating system with a dedicated and fixed set of firewallapplications that implement the network access policy for all VMs inclient 200 (except perhaps VM0 230, which may not have any networkaccess). Firewall VM 250 may provide, to any virtual machine running onclient 200 in which untrusted code is executed or untrusted data isbeing interpreted, restricted access to only those network resourcesdeemed necessary on an as-needed basis in accordance with a policydescribed by policy data stored on client 200.

In another embodiment of the invention, the firewall functionality ofthe system may be co-located and implemented inside either thehypervisor 220 of FIG. 2, or inside the LVM 240 of FIG. 2 (working inconjunction with the hypervisor 220 of FIG. 2), or inside VM0 230 ofFIG. 2 (working in conjunction with the hypervisor 220 of FIG. 2).

Validated Virtual Machines—VVMS

UCVMs are not appropriate to run local applications that interactheavily with each other using local APIs such as COM, as typically thereis no communication channel available for an application running in oneUCVM to communicate with an application running in another UCVM.Embodiments may employ one (or more) special UCVMs called a ValidatedVirtual Machine (VVM) for the purpose of running relatively trustedlocal applications that have complex interactions between theapplications. Such complex interactions are common in enterpriseframeworks containing multiple applications, such as Microsoft's OfficeSuite and IBM's Lotus Notes.

FIG. 2 depicts an exemplary VVM 266 of an embodiment. Note that whileFIG. 2 depicts a single VVM for ease of explanation, other embodimentsof the invention may employ two or more VVMs or no VVMs based upon theparticular needs of the user and/or policies of the organizationresponsible for or the owner of client 200.

Applications need to be signed and configured for co-location in thesame VM by an administrator of client 200 before they can run in VVM266. Inside VVM 266, signed applications can interact with each otherusing all types of APIs and frameworks supported by the OS being used.In an embodiment, the default network access policy of a VVM is to allowaccess to a corporate network only. The IT administrator may increase ordecrease this level of access, subject to certain restrictions.

In an embodiment, specific signed applications or suites (groups ofapplications) that originate from a trusted source (other than theenterprise) may also be designated to run together in a particular VVMresponsible for applications originating from that source. For example,all non-corporate applications that are signed by a specific vendor maybe run together in a single VVM. These applications would then beisolated from corporate applications and general untrusted applications,but not from one another. A specific network access rule that is morepermissive than the “same origin policy” used for web applications andunsigned applications may be used for a VVM. The restricted copy of filesystem 242 exposed to a VVM is similar to that exposed to a generic UCVMin that the restricted copy of file system 242 exposed to a VVMcomprises only those files related to, or required for, performance ofthe applications executing within the VVM.

The Restricted File System Exposed to a VM

FIG. 3 is block diagram of the functional components involved inexposing a restricted copy of file system 242 to different UCVMs (andVVMs) according to an embodiment of the invention. File System Switch310 is software that is configured to provide the newly created UCVMwith access to a copy-on-write clone of the OS image that the UCVM wascreated from once the UCVM has started. The minimal operating system andprogram files 330 in the copy-on-write clone may be created from eitherthe corporate LVM OS image 320 or a separate generic stripped down OSimage 322 which may be created by the IT administrator.

Furthermore, a newly created UCVM is provided a copy of necessary userfiles 340, which are a subset of the user files in file system 242. Thecomposition of necessary user files 340 will be different for each user.The set of files comprising the user files in file system 242 maintainedin LVM 240 are typically those files in the user's home folder, e.g.,c:\Users\<username>. The particular copies of files that are provided toa particular UCVM as necessary user files 340 are the minimum set offiles that are needed by that UCVM to accomplish what the user intendedto do as captured when the target application was being invoked. Forexample, if the user double clicked on a specific MS Word file namedABC.docx at the location c:\Users\<username>\Documents in the filesystem 240 maintained in LVM 240, then necessary user files 340 wouldonly include a copy-on-write clone of the ABC.docx file and only thiscopy-on-write clone of the ABC.docx file is made available in thevirtual c:\Users\<username>\Documents folder made visible to the newlycreated UCVM running the MS Word application. If a program (like MSWord) was started without any association with a file, then necessaryuser files 340 would correspond to an emptyc:\Users\<username>\Documents virtual folder.

Any application running in a UCVM therefore only has access to theparticular set of user files provided explicitly by the user when theprogram was invoked. Subsequently, if the user wants to browse filesystem 242 for another file from within the application (for example, byusing the File→Open menu item of MS Word), then he or she will see arestricted user files directory.

To enable the user to select files from the user's own User Files folderin file system 242 maintained in LVM 240 using an application executingwithin an UCVM, a user interface may be provided to allow the user tobrowse his or her files in file system 242, select one or more of theuser files, and expose a copy of the selected files to the appropriateUCVM. For example, FIG. 4 is a flowchart illustrating the steps involvedin a UCVM obtaining a copy of a new user file maintained in file system242 according to an embodiment of the invention. In step 410, a specialfile is provided to each UCVM. The special file may be provided to theUCVM in a number of different ways, e.g., the special file may beinserted into each folder of the virtual C:\Users\<username>directoryprovided to each UCVM. This special file may be named something akin to“Show All My Files” or the like, as its selection will be used totrigger exposing additional copy-on-write clones of files stored in filesystem 242 to the UCVM.

In step 420, File System Switch 310 detects when the special file isselected by the user. For example, when a program executing within aUCVM browses to the special file, presumably as a result of a userclick, this action may be trapped by File System Switch 310.

In step 430, File System Switch 310 invokes a dialog with LVM 240 thatallows the user to browse the full file system 242 maintained in LVM240. The user may then select a file or folder in file system 242. Notethat at this stage, the user may be granted read access to the full filesystem 242 for purposes of selecting a file or folder, but the user isnot granted write access to file system 242. Therefore, the user isprevented from modifying file system 242 maintained by LVM 240 in anyway.

In step 440, after the user selects a file or folder, a copy of theselected file or folder is created. The copy of the selected file orfolder is then inserted into the restricted file system associated withthe UCVM. As a result of inserting the copy of the selected file orfolder in the restricted file system associated with the UCVM, anapplication executing in the UCVM may have read and write access to thecopy of the selected file or folder in the virtual file system, but isprevented from effecting any change to the original copy of the selectedfile or folder in file system 242 maintained by LVM 240.

The steps of FIG. 4 ensure that files in file system 242 maintained byLVM 240 are not visible to a UCVM without explicit permission from theuser. Malicious code running in a UCVM, for example, cannotprogrammatically access files in file system 242 in LVM 240. Further,malicious code running in a UCVM also cannot render a false userinterface to trick the user into unintentionally providing any userfiles to the malicious code, since all code responsible for renderingthe user interface is maintained within VM0 230, and thus, unreachableand un-hackable by the malicious code.

File System Switch 310 may be implemented in a variety of ways. Forexample, in one embodiment, File System Switch 310 may be implemented bya network file system protocol (NFS or CIFS may be used). A special VM(or LVM 240) may be used as the OS serving the “User Files” shared filesystem. Other VMs “mount” this shared file system using NFS or CIFS (oranother network file system) from the hosting VM. Application softwarein the hosting VM may decide what files are exposed to which VM based oninstructions provided by VM0 230.

In another embodiment, File System Switch 310 may be implemented, inpart, by a proprietary protocol for handling communications between thedifferent UCVMs and File System Switch 310. File System Switch 310, insuch an embodiment, may be implemented as part of a special VM or in LVM240.

Cloning a UCVM from a Template

In an embodiment of the invention, every virtual machine created inclient 220 is instantiated using a template selected from one or moretemplates 238 stored in VM0 230. In an embodiment, each template in oneor more templates is either immutable or may be updated in a verycontrolled fashion. Advantageously, virtual machines may be instantiatedin this fashion with requiring the booting of the virtual machine.

Each of one or more templates 238 may be used to instantiate or create avirtual machine with different characteristics or operationalparameters. The characteristics or operational parameters described by atemplate may be configured, tailored, or suited for a particular contextor type of processing activity. For example, each template may specifywhat type of code is to be run within a virtual machine created usingthe template, a size of the virtual machine created using the template,firewall settings for the virtual machine created using the template,what type of virtual machine (for example, a VVM, UCVM, or a LVM) is thebe created using the template, how changes to a local file system withinthe virtual machine created using the template are to be persisted, andwhat portion, if any, of the network can a virtual machine created usingthe template access.

One or more devices internal to client 200 or externally connected toclient 200 may interact with one or more processes executing in avirtual machine within client 200. In an embodiment, a template mayassign responsibility for a selected set of devices to a virtual machinecreated using the template. In other embodiments, responsibility for aselected set of devices may be assigned to a particular virtual machineby virtue of policy data stored on client 200. Such policy data maydescribe one or more policies provided to client 200 from an owner orresponsible organization of client 200. Policy data of this nature maybe maintained by VM0 230 or LVM 240, for example, in certainembodiments.

In an embodiment, one or more templates 238 may be arranged in ahierarchy such that there is a root node corresponding to a templatehaving a default set of characteristics. The root node may have one ormore child nodes, and each of these child nodes may be associated with atemplate that inherits the properties of the parent template, butcontains additional or changes properties associated with that childnode. Naturally, each child node may also have children, and so thehierarchy of templates may be an arbitrary number of levels deep, whereeach template inheriting characteristics of its parent, but yet eachtemplate is capable of further defining or changing characteristics thatdistinguishes the template over its parent.

Branches of the hierarchy of templates may be associated with, or moreparticularly suited, different types of activity. For example, certaintemplates may be associated with corporate activity, and may thereforespecify characteristics related to virtual machines running corporateapplications. Similarly, certain templates may be associated with theuser's personal application's activity or Internet/Web related activity,and may therefore specify characteristics related to virtual machinesrunning the user's own applications or Internet/Web applicationsrespectively.

FIG. 5 is an illustration of instantiating a plurality of differentvirtual machines using different templates according to an embodiment ofthe invention. In FIG. 5, CVM-0 represents a template that defines avirtual machine having characteristics suitable for running a corporateapplication, PVM-0 represents a template that defines a virtual machinehaving characteristics suitable for running a user application(non-corporate), and WVM-0 represents a template that defines a virtualmachine having characteristics suitable for running an Internetapplication. Other embodiments of the invention may define a variety ofother templates to define different types of templates. In the exampleof FIG. 5, cognitive assist module 236 in VM0 230 may use CVM-0 toinstantiate one or more corporate virtual machines, such as CVM-1,CVM-2, etc. Similarly, cognitive assist module 236 may use PVM-0 toinstantiate one or more personal (non-corporate) virtual machines, suchas PVM-1, PVM-2, etc., and cognitive assist module 236 may use WVM-0 toinstantiate one or more web-based virtual machines, such as WVM-1,WVM-2, etc. As depicted in FIG. 5, each instantiated UCVM connects to anexternal network through Firewall VM 250. Cognitive assist module 236can either create these templates on demand or create and store themwhile monitoring the usage of the client.

Installation of Software

In the normal operation of a typical PC, a fair amount of after-marketsoftware is installed. Such after-market software installed on a PCgenerally falls into one of two categories, namely (a) validatedsoftware (packages or straight executables) installed by the ITadministrator of the PC or (b) end-user installed software (includingweb browser plugins & extensions, more complex software packages that gothrough an explicit install phase, and straight executables that can beexecuted without an explicit installation phase). Note that end-userinstalled software may be signed (by a verifiable, known vendor) orunsigned.

In embodiments of the invention, installation of validated software isperformed as is normally performed today. The IT administrator canmanage corporate validated software using embodiments using similarprocedures as performed today, except that such corporate validatedsoftware are installed in LVM 240 (or if need be, VVM 266).

With respect to end-user installed software, IT administrators have twochoices for how they would like to handle this type of installationusing embodiments of the invention. The first choice is for the ITadministrator to lock down client 200 by disallowing any installation ofend-user installed software. While this is a safer operating decision,this approach may reduce the end-user's productivity because the enduser cannot take advantage of applications that may be otherwise usefulthat have not yet been validated by the IT administrator. The ITadministrator may provide installation support on an individual andas-needed basis whenever a user wishes to install any end-user installedsoftware; however, doing so will increase the cost of support by the ITadministrator.

The second choice is for the IT administrator to allow the user toinstall end-user installed software him or herself using featuresprovided by embodiments of the invention. End-user installed softwaremay include browser plugins, browser extensions, signed and unsignedinstallation packages, and straight executables. Browser plugins areinstalled into an installed browser plugin database that is maintainedin a particular UCVM. The installed browser plugin database may beimplemented, in an embodiment, using file and registry diff store 820shown in FIG. 8, which is an illustration of safely installing anuntrusted application according to an embodiment of the invention of theinvention. During installation of a plugin, the installed browser plugindatabase is also updated to record the domain that was used to initiatethe plugin install. Presumably, this is the web page that contains anelement or component that requires the plugin to render the completecontent in the web page. Subsequently, the web browser loads aninstalled plugin into a web HTML/JS engine instance (which runs inside aUCVM) only if the domain of the web page to be displayed by the UCVMmatches a domain, recorded in the plugin database, associated with theinstalled plugin. A plugin that is used by multiple sites is installedonly once, but is associated with multiple domains. Popular plugins likeFlash may be pre-installed in certain embodiments.

Browser extensions may be installed into a web browser's extensiondatabase that is maintained in a particular UCVM. During runtime,browser extensions are treated like web applications in that eachbrowser extension is run inside its own UCVM. In an embodiment, the webbrowser extension database and the installed browser plugin database maybe implemented in the same database in a single UCVM.

Signed installation packages may be run and the resulting installationmay update either the LVM image or the Generic Windows image based on apolicy set by the IT administrator.

Unsigned installation packages go through a virtual install. The virtualinstallation of unsigned installation packages will be described withreference to FIG. 8, which is an illustration of safely installing anuntrusted application according to an embodiment of the invention of theinvention. A registry and program files change set is created and storedin file and registry diff store 820. Start-menu and desktop changes bythe installer are captured in a special folder which contains desktopand start menu items for all user-installed applications. Subsequently,if an unsigned application is run, it is run in a UCVM cloned from theGeneric Windows image all by itself. Virtual disk 810 in FIG. 8 is thenormal virtual disk of the UCVM. DiffStore 820, which furthervirtualizes the file system and the registry as seen by the applicationsof UCVM, is typically implemented as a separate module outside of thenormal block level virtual disk store.

Signed and unsigned executables may be run in a UCVM. Such a UCVM may becreated on demand and destroyed after its use is ended by embodiments.

Managing Web Cookies and Caches

A web cookie (or simply “cookie”) is a piece of text stored on a user'scomputer by their web browser. A cookie can be used for authentication,storing web site preferences, shopping cart contents, the identifier fora server-based session, or anything else that can be accomplishedthrough storing text data.

While the actual cookie itself is not visible to the user, the userwould notice a difference in the user experience of interacting with aweb site if cookies could not be saved between visits to the web site.Accordingly, embodiments of the invention provide mechanism to storecookies before a UCVM is destroyed, so that the next time the uservisits the web site using a web browser running in a different UCVM, anycookies that have been stored and are associated with that web site maybe injected into the new UCVM.

Similarly, to provide the best user experience, it would be advantageousto carry over the cache of a web browser for a particular web domainfrom one UCVM to the next, so that the next time the user visits the webdomain using a different UCVM, there is no a delay in displaying contentdue to an unpopulated cache. Thus, embodiments of the invention providemechanism to store the web cache of a web browser for a web domainbefore a UCVM is destroyed, so that the next time the user visits theweb site using a web browser running in a different UCVM, the cache ofthe web browser need not be warmed (i.e., repopulated), as the cache inthe new UCVM has been updated to contain all the objects the cachepreviously contained in the prior, and now destroyed, UCVM used to visitthe web domain.

To provide a concrete example with reference to the example of FIG. 2,assume that a user initially transparently uses UCVM 260 to run a webbrowser to visit web site A. When UCVM 260 is destroyed, any cookies andcache files are extracted and saved. Thereafter, assume the usertransparently uses UCVM 262 to run a web browser to visit web site B. Asweb site B is hosted by a different web domain than web site A, thepreviously stored cookies and cache files associated with web site Awill not injected into UCVM 262. Thereafter, if UCVM 262 is destroyed,then any cookies and cache files are extracted and saved. At a laterpoint in time, if the user thereafter transparently uses UCVM 264 to runa web browser to visit web site A, then the previously stored cookiesand cache files associated with the web domain of web site A will beinjected into UCVM 264. This allows the web browser running in UCVM 264to visit web site A to appear, to the user, to have the same state ofthe prior web browser used to visit web site A, even through differentvirtual machines are used between visits. Note that no portions of thefile system are saved between visits to a web site; only the state ofthe web session is saved.

In one embodiment, the cookies and cache information is captured in DiffStore 820 associated with the URL of the website. In each visit to thesame URL, the UCVM utilizes the same Diff Store presenting the cookiesand caches to the UCVM. In another embodiment, the cookies and cachefiles can be captured at the end of the session and saved to the clientsystem's core file system in a special folder. On visiting the same URLagain, the cookies and cache can be re-injected into the file system ofthe UCVM.

Efficient Physical-to-Virtual Disk Conversion

Platform virtualization is performed on a given hardware platform byhost software (a control program), which creates a simulated computerenvironment, a virtual machine, for its guest software. A hypervisor,also called virtual machine manager (VMM), is one of many hardwarevirtualization techniques that allow multiple operating systems, termedguests, to run concurrently on a host computer. The hypervisor presentsto the guest operating systems a virtual operating platform and managesthe execution of the guest operating systems. A guest OS executes as ifit was running directly on the physical hardware. Access to physicalsystem resources such as the network access, display, keyboard, and diskstorage is suitably virtualized so that guest OS does not know these arevirtual devices.

Generally, there are two types of hypervisors. Type 1 (or native, baremetal) hypervisors run directly on the host's hardware to control thehardware and to manage guest operating systems. A guest operating systemthus runs on another level above the hypervisor. Type 2 (or hosted)hypervisors run within a conventional operating system environment. Withthe hypervisor layer as a distinct second software level, guestoperating systems run at the third level above the hardware. In otherwords, Type 1 hypervisor runs directly on the hardware; a Type 2hypervisor runs on another operating system, such as Windows.Embodiments of the invention may use any type of hypervisor. Thus,hypervisor 220 in FIG. 2 may either be a Type 1 or a Type 2 hypervisor.

A virtual disk image is a file on a physical disk, which has awell-defined (published or proprietary) format and is interpreted by ahypervisor as a hard disk. In terms of naming, a virtual disk image mayhave a specific file type extension, e.g., .vmdk for VMware VMDK, .vhdfor Xen and Microsoft Hyper-V, and .vdi for Oracle VM VirtualBox.

There are two approaches employed for storage allocation by priorhypervisors, namely, (1) pre-allocate the entire storage for the virtualdisk upon creation and (2) dynamically grow the storage on demand. Inthe former approach involving pre-allocation, the virtual disk may beimplemented as either split over a collection of flat files (typicallyone is 2 GB in size) or as a single, large monolithic flat file. In thelatter approach involving on-demand growth, the virtual disk may also beimplemented using split or monolithic files, except that storage isallocated on demand.

There are two modes in which a disk can be mapped for use by a virtualmachine. In a virtual mode, the mapped disk is presented as if it is alogical volume, or a virtual disk file, to the guest operating systemand its real hardware characteristics are hidden. In a physical mode,also called the pass through mode, the hypervisor bypasses the I/Ovirtualization layer and passes all I/O commands directly to the disk.

A virtual machine (VM) is a software implementation of a machine (i.e. acomputer) that executes programs like a physical machine. Virtualmachines allow the sharing of the underlying physical machine resourcesbetween different virtual machines, each running its own operatingsystem. The software layer providing the virtualization is called ahypervisor, such as hypervisor 220 in FIG. 2.

Virtual machines each require their own image of the operating system.The guest OS and host OS typically do not share the OS image, even ifthey are the same OS. This is problematic for several reasons. First, ifa user wishes to run 10 different virtual machines, then she willrequire 10 different copies of the OS for the guest OSs, which requiresan undesirable amount of storage to maintain. As she is already runningone virtual machine at the host, the total number of different copies ofthe OS required would be 11. Second, the OS for a VM has to be createdeither by installing a new OS or shipping a copy of the OS fromsomewhere else, which is burdensome for those who do not have access toOS images. Further, it is also time consuming to install a new OS orship an OS image, which is typically quite large. A third problem isthat any software present in the host OS (such as a printer driver) willnot be available in a guest OS unless it is installed again.

Shadow Copy (Volume Snapshot Service or Volume Shadow Copy Service orVSS) is a technology included in Microsoft Windows that allows takingmanual or automatic backup copies or snapshots of data (termed “shadowcopies”), even if it has a lock, on a specific volume at a specificpoint in time over regular intervals. VSS operates at the block level ofthe file system. Shadow Copy is implemented as a Windows service calledthe Volume Shadow Copy service. Software VSS provider service is alsoincluded as part of the Microsoft Windows OS to be used by Windowsapplications. Shadow Copies can be created on local and external(removable or network) volumes by any Windows component that uses thistechnology, such as when creating a scheduled Windows Backup orautomatic System Restore point.

Snapshots have two primary purposes. First, they allow the creation ofconsistent backups of a volume, ensuring that the contents cannot changewhile the backup is being made. Second, they avoid problems with filelocking By creating a read-only copy of the volume, backup programs areable to access every file without interfering with other programswriting to those same files. Through the integration between the VolumeShadow Copy Service, hardware or software VSS providers, applicationlevel writers and backup applications, VSS enables integral backups thatare point in time and application level consistent without the backuptool having knowledge about the internals of each application. The endresult is similar to a versioning file system, allowing any file to beretrieved as it existed at the time any of the snapshots was made.Unlike a true versioning file system, however, users cannot trigger thecreation of new versions of an individual file, only the entire volume.

Embodiments of the invention overcome this limitation by creatingvirtual disks based on VSS shadow copies. FIG. 6 is an illustration of avirtual disk based on VSS shadow copies according to an embodiment. Thevirtual disk of FIG. 6 allows for many guest OSs running on the samehost to share the same OS copy with the host OS. VSS shadow copies maybe created fast and efficiently. Creating virtual disks on top of VSS isalso a very fast operation, which means that VMs (with same OS as hostOS) can be created very efficiently. Shadow copies are also maintainedcheaply by windows OS by keeping the changes since the time shadow wascreated. Hence, the disk usage of multiple VMs is reduced substantially.VMs can also be maintained very efficiently since VSS snapshots can beupdated once and have the changes reflected in all VMs. Since a VSSshadow copy contains all the software the user has installed on themachine at the time of the VSS shadow copy creation, virtual disks alsoreceive access to all the software. Moreover, the version of thesoftware, including any patches installed, is exactly the same. Inaddition to all the software, user documents are also visible to virtualmachines. A virtual disk of an embodiment is an accurate point-in-timecopy of host physical disk.

In an embodiment where VSS snapshots are read-only, a ‘Delta Store Disk’may be attached to the virtual disk. The Delta Store disk is used tocapture all the changes being made to the virtual disk.

Security Afforded by Embodiments

Embodiments of the invention provide a secure environment to preventmalicious code from affecting any lasting change in a computer system.Arbitrary code (either a web application or a native executable) runsinside an isolated operating system running on an isolated virtualmachine. This code has no access to any other application (either anative application or a web application) being run by the user becausethose applications run in other operating systems running in separatevirtual machines. Moreover, arbitrary code has access to only thespecific part of the file system that is needed for correct execution ofthe code. Access to additional parts of the file system has to beprovided by code that runs in VM0 (which is secure and fortified againstunauthorized intrusion) and any increased access needs explicitauthorization from the human user.

Specific trusted code that needs to interact in a complex way with otherapplications may be explicitly designated to run together inside thesame designated VM. This type of VM also has limited access to the filesystem.

All code and files have limited network access to just what that codeneeds for its correct execution. All virtual machines are created fromtemplates stored in VM0 which are either immutable or can be updated ina very controlled fashion. Consequently, if a security bug exists in apiece of code, the effect of the security bug is isolated (“spacelimited”) because the compromised code has access to only a limited partof the file system, the network, devices, etc. Moreover, the effect ofthe security bug is “time limited” because the virtual machine that hasbeen compromised will be subsequently discarded and a new virtualmachine is created for future application instances from a cleanimmutable VM template.

Using Policy Data to Manage the Deployment of Virtual Machines

Embodiments allow code that originates from arbitrary external sourcesto be safely executed by a client. In this way, digital content ofunknown trustworthiness may be safely received and potentially executedand/or interpreted by a client without incurring the risk that thedigital content contains malicious code that could cause undesirableconsequences.

The ‘digital content’ received by the client from an external source maycorrespond to any type of digital data, such as executable code ornon-executable, interpreted data for example. Since malicious code maybe carried within certain types of non-executable data and subsequentlyspread when the data is interpreted by applications, embodiments treatall incoming digital content as being capable of containing maliciouscode, even if the digital content is not in a recognized executableform. Non-limiting, illustrative examples of digital content include an“.exe” file, an application, a collection of applications designed torun together, a portion of an application, an email attachment, a slidepresentation, a text document, and a web page (which essentially is aportion of an application, namely a web browser). Even though the emailattachment, the slide presentation, and the text document, in and ofthemselves, are not executable files, embodiments of the invention treatthese forms of digital content as potentially carrying malicious code.

To manage the risk posed by receiving digital content of unknowntrustworthiness, any digital content received by a client is stored inone or more virtual machines. In an embodiment, digital content receivedfrom an external source may immediately be stored in one or more virtualmachines upon receipt. Alternately, digital content received from anexternal source may be stored in an intermediate location, such as alocal cache, prior to storing the digital content in a virtual machine.

While embodiments are configured to process all digital contentoriginating from an external source in a virtual machine, the complexityof determining in which virtual machine the digital content should bestored and how that virtual machine should be configured is hidden fromthe user whenever possible or appropriate. To accomplish this goal,techniques are discussed herein for programmatically managing aplurality of virtual machines on the client to accommodate the widevariety of use cases for receiving digital content at a client. However,in some cases, explained in more detail below, it may be appropriate toinform the user of certain activity concerning a virtual machine, suchas when obtaining express permission from the user is advisable beforeperforming an action.

Certain sources of digital content are more trustworthy than othersources. For example, the web site of a bank or Fortune 500 company maybe more trustworthy than the web site of a smaller company or lessorknown organization. Also, applications may have different operatingneeds, e.g., certain applications may be designed to work closely withother applications or require access to network resources. Thus, in anembodiment, the attributes of each virtual machine are specificallytailored to reflect the type of digital content and/or applicationsoperating or stored therein.

To illustrate how one embodiment operates, when a client determines thatdigital content, originating from an external source, is to be receivedor processed by the client, the client may identify, without humanintervention, one or more virtual machines, executing or to be executedon the client, into which the digital content is to be received. To doso, the client may consult policy data, such as policy data 239 storedat client 200 of FIG. 2, to determine a placement policy, a containmentpolicy, and a persistence policy used in identifying the one or morevirtual machines into which the digital content is to be received.

The policy data may be used to specifically tailor the operation of eachvirtual machine to reflect the type of digital content and/orapplications operating or stored therein. The placement policyidentifies a particular virtual machine into which the digital contentis to be stored, the containment policy identifies what networkresources and client resources the particular virtual machine canaccess, and the persistence policy identifies whether data (or a part ofit) stored in the particular virtual machine is persistently stored.Naturally, the placement policy, containment policy, and persistencepolicy are, to a certain extent, intertwined, as the resources a virtualmachine may access and whether data stored therein is persisted willaffect what applications/digital content are appropriate to residetherein.

In an embodiment, each of the placement policy, the containment policy,and the persistence policy may consider a variety of different factors.For example, the placement policy, the containment policy, and/or thepersistence policy may consider a historical record of use for theclient in identifying a virtual machine. The evaluation of a policy mayinvolve consulting a historical record of how the client, orapplications running thereon, has been used. In this way, if aparticular action has been judged to be more safe (or less safe) over aperiod of time, the manner in which the action is handled by the policymay evolve over time. To illustrate, in an embodiment, if a particularnetwork resource, such as an affiliate corporate web page, isdemonstrated to be sufficiently safe over a period of time, then thisweb page may be processed using relaxed restrictions, e.g., by a webbrowser in a virtual machine already handling another trusted web pageas opposed to instantiating a new virtual machine to handle theaffiliate corporate web page. On the other hand, if the historicalrecord of use demonstrates that an action involving a particular networkresource or client resource may pose some risk to the client, then thepolicy may subsequently handle this action more sensitively than before,e.g., by assigning code to handle the particular network resource orclient resource in a dedicated virtual machine with restricted access toclient and network resources.

As another example of the types of factors which may be considered by apolicy, one or more of the placement policy, the containment policy, andthe persistence policy may consider a current physical location of theclient or to which networks the client currently has access inidentifying one or more virtual machines which should be used to receivecontent. In this way, which networks are available to the client, the IPaddress assigned to the client, the current location of the client basedon global positioning service (GPS) data, and the current location ofthe client based on an IP address or which networks are available to theclient may all be considered when determining which virtual machineshould receive digital content and what restrictions should be placed onthat virtual machine. In this way, when the client is physically locatedin an area deemed safe (such as a work office or home), digital contentreceived by the client may be handled by a virtual machine having a setof lesser restrictions than when the client is physically located in anunknown area.

As another example of the types of factors which may be considered by apolicy, one or more of the placement policy, the containment policy, andthe persistence policy may consider the proximity of the client to awireless device, such as a Bluetooth enabled cell phone. For example, ifthe client is not within a configurable distance to the cell phone ofthe user of the client, then the client may receive digital contentusing a set of greater restrictions, e.g., code executing in all virtualmachines may be denied access to certain client resources and/or allnetwork resources. Embodiments may determine whether the client iswithin a configurable distance to a wireless device using a variety ofdifferent methods, such as accessing the wireless signal strengthbetween the client and the wireless device.

In an embodiment, at least a portion of the policy data, used inidentifying one or more responsible virtual machines to receive digitalcontent, is obtained from a remote server after the client determinesthat digital content is to be received from an external source. In thisway, policy data may be sent, as needed, from an IT administrator to theclient. The client may treat any policy data already residing on theclient in the same manner as policy data retrieved from a remote server.For example, when a user of the client performs an action, the clientmay consult a remote server to see if the remote server has anyadditional policy data regarding this action. Following this procedure,an IT administrator can maintain a high level of control on how theclient will manage virtual machines running on the client. This enablesthe IT administrator to make adjustments to the security model followedby the client in real-time. The client may interact with a humanoperator at a remote location to obtain additional policy data or mayinteract with a remote automated system, without human intervention, toobtain the additional policy data. Note that certain embodiments may beconfigured to consult a remote server for policy data only when acertain configurable action is taken. Therefore, in certain embodiments,the client need not always contact a remote server to determine ifadditional policy data is available each time that the client is toreceive new digital content.

In an embodiment, the policy data may specify that the virtual machineassigned to receive digital content can only access a limited subset ofthe metadata properties for a client resource or a network resource. Forexample, a virtual machine may not be capable of determining what localwireless networks are available in the vicinity or whether the networkcard of the client is of a particular type. In this way, the amount andtype of information exposed to a particular virtual machine may becontrolled to a fine level of granularity.

Use of the placement policy, the containment policy, and the persistencepolicy by certain embodiments will be discussed in further detail below.

Placement Policy

The placement policy identifies a particular virtual machine into whichthe digital content is to be stored. The particular virtual machineidentified by a placement policy in which digital content is to bestored may be an existing virtual machine or a new virtual machine thathas not yet been instantiated. In the case where the placement policyspecifies that the digital content should be received by a virtualmachine that has not yet been instantiated, either the placement policyitself or some other location in the policy data will identify atemplate for use in instantiating the particular virtual machine. Theidentified template will describe characteristics of a virtual machinesuitable for receiving the digital content.

The placement policy may weigh a variety of different considerations indetermining which virtual machine should store the digital content sothat the digital content may be safely executed, interpreted, and/orprocessed. For example, a placement policy of an embodiment may assignany file having a certain name or certain attributes to a virtualmachine having certain characteristics. To illustrate, a placementpolicy may indicate that all signed executable files from an internalorganization or company are to be assigned to a virtual machine having aspecified set of characteristics. As another example, the placementpolicy may instruct untrusted applications to execute in separatevirtual machines so that each untrusted application is isolated fromother applications and data of the client.

The placement policy of an embodiment may identifies a plurality ofclasses of virtual machines, where each class of the plurality ofclasses is associated with a different trust level for external sourcesof digital content. Code executing in a virtual machine cannot accessexternal sources associated with less trustworthy external sources ofdigital content. For example, assume there are three classes of virtualmachines, where the first class of virtual machines is designed to runweb browsers accessing web sites of financial institutions and emailproviders, the second class of virtual machines is designed to run webbrowsers accessing web sites of Fortune 500 companies, and the thirdclass of virtual machines is designed to run web browsers accessing allother web sites. In this example, a web browser executing in a virtualmachine that is associated with the third class cannot access any websites from Fortune 500 companies or financial institutions and emailproviders. Similarly, in this example, a web browser executing in avirtual machine that is associated with the second class cannot accessany web sites from financial institutions and email providers.

The placement policy of an embodiment may identify the particularvirtual machine into which the digital content is to be received byobserving application dependencies. Such a policy recognizes that insome instances, it is helpful or even necessary to execute certainapplications within a single virtual machine. For example, certainproviders of software applications may design their softwareapplications do work together or integrate with each other to a highdegree. In this case, it would be advantageous to have applications thatare designed to work together to run within a single virtual machine.One way for the placement policy to make this determination would be toask the user whether an application being installed is dependent uponanother application already installed at the client to ensure that bothapplications may be run in the same virtual machine. While this doesexpose the notion of a virtual machine to the user, a user need onlymake a decision of this nature when an application is installed on theclient, and thus, this decision may be made by IT administrators orother knowledgeable personal rather than relying upon the end user ofthe client to make such a decision.

Alternatively, determining whether an application being installed isdependent upon another application may be made programmatically byexamining the dependencies during the installation of that application.For example, during the installation of application A, the installprocess may check if module B is already installed or may require thatmodule B already by installed. In this example, the placement policy maydetermine then that application A has a dependency with module B and maytherefore allow application A to run in same virtual machine as moduleB.

To illustrate another example, it is initially noted that there need notbe a one to one correspondence between a web browser and a web page. Forexample, a web browser may comprise many tabs, and each tab may displaya different web page. In addition, each web browser may have a varietyof different plug-in and/or associated programs which may be treated asor considered a separate application. Since a web browser may displaymultiple web pages of varying trust levels, it is desirable toaccommodate a web browser having multiple tabs without requiring thatthe web pages displayed by each tab reside in the same virtual machine.For example, if a web page contains malicious code, then it would bebeneficial to execute it in a different virtual machine from the virtualmachine containing the web page of your bank. Therefore, in anembodiment, the placement policy may specify that web page of certainsources should be received in a separate virtual machine. While the usermay see a single web browser having two tabs, on the back end this maybe implemented in two separate virtual machines that each execute a copyof the web browser and possess one web page to be shown in associatedwith one tab of the web browser. A practical implementation of web pageplacement may use a VM per web-site placement policy.

These are merely examples of how a placement policy may be implemented.It is contemplated that actual implementations of a placement policywill be configured based upon the particular needs and concerns of theend user. The containment policy of certain embodiments will now bepresented in greater detail.

Containment Policy

The containment policy identifies what network resources and clientresources a particular virtual machine can access. Network resources, asbroadly used herein, refers to any resource that is external to theclient while client resources, as broadly used herein, refers to anyresources that is internal to the client. A client resource may includeany device, component, and/or data residing on or accessible to theclient, such as a digital camera, a network interface card, a digitalclock, the current time, files, pictures, and email.

The containment policy is used to ensure that code running within avirtual machine has access to only those resources deemed necessary fornormal and intended operation. For example, email attachments should notneed access to the Internet (generally speaking), and so they should beopened in a virtual machine that is configured such that it does nothave access to the Internet. Contain policies may be used to ensure thatthe resources of the client that are accessible to a virtual machine arethose resources necessary to perform the activity intended to beperformed within, e.g., a virtual machine instantiated to open a filemay only have access to resources necessary to open, view, and edit thefile.

In an embodiment, the containment policy may specify what portion of thenetwork that is available or exposed to code executing within a virtualmachine. For example, the containment policy may specify that codeexecuting within a particular virtual machine may access no networkresources, all network resources, or a subset of the network resources.Thus, a containment policy may specify that code executing within avirtual machine may access a first set of network resources and may notaccess a second set of network resources. Embodiments may specify whatparticular network resources are available to a virtual machine usingany level of granularity, e.g., only certain types of network resourcesmay be exposed, only certain properties of network resources may beexposed, or only certain portions of the network may be exposed.

In an embodiment, enterprise applications may be grouped intocollections. Groupings may be based on a variety of factors, such as jobfunctions or business unit, for example. Each grouping of applicationsmay be executed within a single virtual machine according to anembodiment.

To illustrate the interaction between the containment policy and clientresources, the containment policy of an embodiment identifies eachclient resource accessible to a virtual machine. For example, acontainment policy may specify whether code executing in the particularvirtual machine can perform one or more of the following actions: accessa USB port on the client, perform a copy operation or a paste operation,access a network to which the client is connected, access a GPS deviceof the client, location information for the client, or tilt informationfor the client, access a printer or facsimile machine to which theclient is connected, and access a digital camera or screen data for theclient. Note that these exemplary actions are not meant to provide anexhaustive list, as a containment policy may be used to specify, withparticular specificity, which client and network resources may beaccessed by code executing within a virtual machine. In this way, if anew client resource becomes available, such as fingerprint scanningdevice, the containment policy may be updated to reflect the new clientresource available to the client.

In an embodiment involving the receipt of executable code at a client,the containment policy may specify that the executable code is deniedaccess to a user file without first obtaining a user's permission toallow the executable code to access the user file. In this way, virtualmachines may be configured to allows request permission each timeexecutable code therein access a user file, thereby allowing the user tobe informed of the intentions of the executing code and presumablyprevent unauthorized access to the user's own files. Such a permissionscheme might be implemented naturally as part of the normal user workflow of picking a file to open by running the permission code in a cleanprotected VM separate from the VM running the untrusted code which ismaking the request.

To illustrate the interaction between the containment policy and networkresources, the containment policy of an embodiment identifies whethercode executing in a particular virtual machine can one or more networksaccessible to the client. As another example, the containment policy ofan embodiment identifies which, if any, objects stored over a networkthe virtual machine can access. For example, a virtual machine may berestricted to access a specified set of objects or files on a particularserver or a particular set of web pages.

In an embodiment, the containment policy may consider any number offactors, including but not limited an identity of the user of theclient, a set of properties of the digital content, a physical locationof the client, the current time, a holiday schedule, and a set ofadministrator-specified policy rules. In this way, the containmentpolicy may assign a virtual machine having more restrictions than usualto receive digital content when the digital content is deemed morelikely to contain malicious code. For example, it may be deemed likelythat digital content contains malicious code when it is received by theclient outside of normal business hours, over a holiday, at a time whenthe client is outside of the user's home or work office, or when thedigital content has certain suspicious properties. In this way, thecontainment policy may assign suspicious digital content to be receivedin a virtual machine having additional restrictions appropriate for suchsuspicious digital content.

These examples of how a containment policy may operate and merelyillustrative of some examples and are not intended to be an exhaustivelist, as actual implementations of a containment policy will beconfigured based upon the particular needs and concerns of the end user.The persistence policy of certain embodiments will now be presented ingreater detail.

Persistence Policy

In an embodiment, the persistence policy identifies whether data storedin a particular virtual machine is persistently stored. The policygrapples with the issue of whether or not to save state created byuntrusted code and if so, whether the state should be stored in anisolated manner or merged back into the main file system of thecomputer. On one hand, to provide a convenient user experience, it maybe helpful to persistently store cookies for a web site. On the otherhand, it would not be desirable to persistent malicious code, such as akey logger, that was inadvertently introduced into a virtual machine bymalware downloaded into and run in the affected virtual machine.

The persistence policy, hand in hand with the placement policy, shouldbe designed to ensure that any potentially malicious code is notpersistently stored, or in the alternative, persistently stored in anisolated way. This way, if malicious code, such as a key logger, ispersistently stored, and in any future invocation (execution orinterpretation), it is invoked (executed) in the context of a possiblynew virtual machine instance separate from any other code, therebynullifying the risk presented thereby.

To illustrate an illustrative persistence policy, in an embodiment onlycookies and cache files are persistently stored in a virtual machine inwhich a web browser executes. Further, the cookies and cache filesassociated with a particular web site are only inserted to a virtualmachine that is intended to execute a web browser displaying that website. Thus, cookies and a cache file associated with site A would not beinserted into a virtual machine instantiated to run a web browser todisplay web site B, but would be inserted into a virtual machineinstantiated to run a web browser to display web site A.

The above discussion of a persistence policy is exemplary of certainembodiments and is not intended to describe all implementations of apersistence policy, as a persistence policy will be configured basedupon the particular needs and concerns of the end user.

Unified Display

Even though there may be a plurality of virtual machines executing atthe client, this complexity need not be exposed to the end user of theclient. Thus, the end user should be presented visual content generatedfrom each virtual machine executing on the client in a unified manner topresent a single, cohesive presentation to the end user of the client.The presentation of the content should be seamless and close to nativeas possible.

For example, the end user of the client should interact with a webbrowser that looks like a known web browser, even though the webbrowser, at the back end, is implemented using a plurality of virtualmachines to execute copies of the web browser and different web pagescorresponding to each tab of the web browser.

Seamless Management of Untrusted Data Using Virtual Machines

As previously explained above, data may contain malicious code which canbe used to compromise a system. Thus, computer systems of an embodimenthandle data of unknown integrity with care to ensure the security andprivacy of a computer. Embodiments employ approaches for identifyingdata which is deemed “untrustworthy.” As an example, data which isretrieved by the computer system from an external network may beconsidered untrusted data.

Once data enters into a computer system, the data may interact withprocesses of the system. For example, untrusted data may interact withdifferent types of mime-type handlers, the user, and/or a searchindexer. Embodiments of the invention strive to allow the user to usethe untrusted data, while still ensuring the untrusted data is ascontained as possible to combat any malicious code contained therein.Containing the untrusted data would be trivial if the user was preventedfrom using any untrusted data; however, such an approach would frustratethe user by preventing many common use cases of the computer system.Advantageously, embodiments provide a user experience that is as nativeas possible to allow the user to have meaningful interaction withuntrusted data, but in a safe manner that limits the exposure of clientresources to the untrusted data.

When an action is requested to be performed on untrusted data,embodiments may handle the request based on the perceived intent of theuser and the amount of risk presented by the requested action.Naturally, a requested action may simply be granted or denied. However,embodiments also allow for the action to be performed in a restrictedmanner. In such a case, the user may be completely unaware that therequested action was performed in a restricted manner, since the detailson how the action was performed by the computer system were not exposedto the user.

To illustrate a concrete example, assume that a user wishes to view atext document that was retrieved over the Internet. Embodiments of theinvention may consider the text document retrieved from the Internet asuntrusted data. When the user clicks on a displayed icon representingthe text document, the user's click causes a request to view the textdocument to be generated. This request may be redirected by embodimentsof the invention so that the request is processed within a differentvirtual machine from which the request originated. The virtual machinein which this request is processed may have no access to any network,such as the Internet or any corporate network, as well as have no accessto any file system. In this way, the request to view the text documentmay be safely processed in an environment which prevents any maliciouscode, embedded within the text document, from gaining access to the filesystem or communicating outside of the computer system. The user neednot have any idea that the request to view the text document wasredirected to a different virtual machine. From the user's perspective,the request to view the text document was seamlessly processed asexpected.

FIG. 10 is a flowchart illustrating the high level functional steps ofmanaging untrusted data according to an embodiment of the invention. Asshown in FIG. 1, initially, in step 1010, a policy is applied toidentify untrusted data. In an embodiment, step 1010 may be performed bycognitive assist module 236 applying a policy stored in policy data 239.Thereafter, in step 1020, a policy is applied to determine how toprocess an action directed against untrusted data. Note that any amountof time may pass between the performance of step 1010 and step 1020.Each of the steps of FIG. 10 shall be discussed below in further detail.

Untrusted Data

In step 1010, a policy is applied to identify untrusted data. In anembodiment, step 1010 may be performed by cognitive assist module 236applying a policy stored in policy data 239. However, other embodimentsmay store policy data describing one or more policies for identifyinguntrusted data in locations other than VM0 230. Also, in otherembodiments, one or more different functional components, other thancognitive assist module 236, may identify untrusted data in step 1010.

Untrusted data shall chiefly be discussed herein in terms of beingembodied as files which reside on a storage medium, such as a hard-diskdrive. Untrusted data, at a high level, is any data, such as a file,which has not previously been identified as being trusted. Differentembodiments or implementations may define what constitutes untrusteddata differently. For example, untrusted data may include any data whichoriginates outside of a computer system or a trusted domain, such as acorporate network. Untrusted data may be introduced into a computersystem a variety of different ways, such as through a DVD, a FireWirecable, a network, a USB port, to name but a few examples.

Alternately or additionally, any data that is created by a program thathas been deemed untrustworthy may also be considered untrustworthy. Alist of untrustworthy programs may be maintained by embodiments, and anydata created by any untrustworthy program on the list will be considereduntrustworthy. Similarly, a list of trustworthy programs may bemaintained by embodiments, and any data created by a program not on thelist of trustworthy programs may be deemed untrustworthy.

Untrusted data may be identified by virtue of the data being created ina specific location, such as a particular folder of a file directory.For example, files created within a network folder in which multipleentities (potentially unknown entities) have write access may be riskyto consume, and so any file written to or saved in such a location maybe deemed untrustworthy. In certain embodiments, any data that iswritten by a process having access to the Internet or other specificresources may be considered untrusted data. Any data that is accessed bya particular type of program may also be deemed untrusted data.

An executable file may be deemed untrustworthy based on its behavior.For example, if the executable file opens a connection to the Internetand communicates with untrusted data or an untrusted network, then theexecutable file or action may be deemed untrustworthy and subsequentlyany data written by the executable file is deemed untrusted. Thus,embodiments may maintain a list of unacceptable behavior for executablefiles, and if an executable file behaves in an unacceptable manner, thenthe executable file will be deemed untrustworthy.

In an embodiment, upon determining that an action is untrustworthy, aresponsive action may be performed. To illustrate, embodiments may denyaccess to a file is the request is considered untrustworthy. Also,characteristics about any action deemed untrustworthy may be describedin an entry that is added to an audit log to facilitate future analysis.In an embodiment, if an action is deemed untrustworthy, then an alert toan authority (such as an authentication server, cognitive assist module236, or other such entity responsible for authentication and/ordetermining permission levels) may be issued to request permission toaccess the file.

In an embodiment, if a process reads or otherwise consumes any untrusteddata, then the process itself becomes untrusted. Moreover, any datawritten by the untrusted process would also be deemed untrusted data. Toillustrate a concrete example, assume that a particular “.docx” file isdeemed untrustworthy. In an embodiment, if an instance of Microsoft Wordis used to open the untrustworthy “.docx” file, then the instance ofMicrosoft Word, as well as any documents written by the instance, willbe deemed untrustworthy.

Any data that would otherwise be considered untrusted may be consideredtrustworthy if the data is signed by an appropriate authority, such asan IT administrator or the like.

The approaches described above may be combined in any manner and in anarbitrarily complex fashion. Thus, embodiments may employ any number ofapproaches for identifying untrusted data. Certain embodiments mayemploy policies that consider one or more factors in identifyinguntrusted data, and each factor in such a policy may be, but need notbe, given a different weight.

Ensuring Untrusted Data is Properly Identified

In certain embodiments, data identified as untrusted data in step 1010may be associated with a record (hereinafter an “untrustworthy record”)to label the data as untrusted data. This label may be used to ensurethat the data remains identifiable as untrusted, regardless of whetherthe untrusted data is renamed, copied, compressed, uncompressed,decomposed into smaller portions, comprised within a larger entity, etc.

For example, assume that a zip file is deemed untrustworthy. Embodimentsof the invention may associate an untrustworthy record with the zipfile. If the untrusted zip file is unzipped, then the contents of thezip file should also be deemed untrustworthy. Therefore, theuncompressed contents of the zip file will also be associated with anuntrustworthy record. Similarly, renaming the untrusted zip file wouldnot disassociate the untrustworthy record from the untrusted zip file.

As untrusted data may contain potentially malicious code, any processwhich consumes untrusted data subsequently should be considereduntrusted as well, since it may have been corrupted. Thus, embodimentsof the invention follow a “transitive law of untrustworthiness” byassuming that any process that reads, consumes, or uses untrusted databecomes itself untrusted. The untrusted process would then be associatedwith an untrustworthy record. Moreover, any data written by an untrustedprocess is considered to be untrusted data, and thus, would beassociated with an untrustworthy record.

To illustrate an example of this, assume that a text document has beendeemed untrustworthy and thus, is associated with an untrustworthyrecord. If an instance of a Microsoft Word application reads theuntrustworthy text document, then an embodiment will associate thatinstance of the Microsoft Word application with an untrustworthy recordto identify that instance as being untrustworthy. If the untrustedinstance of the Microsoft Word application subsequently saves anotherdocument, then that new document would be considered an untrusted fileand be associated with an untrustworthy record.

In an embodiment, each untrustworthy record may contain metadata aboutthe circumstances which lead the associated data to being labeleduntrustworthy. For example, an untrustworthy record may identify how thedata entered into the computer system. In this way, embodiments of theinvention may examine untrustworthy records to extract certain metadatathat may be used in determining how to handle the untrusted data. Forexample, embodiments of the invention described below may employpolicies which handle untrusted data different based on how theuntrusted data entered the computer system. In this way, untrusted datathat enters into a computer system via a perceived lower risk route(such as via a CD or DVD) may be handled in a different manner thanuntrusted data that enters into the computer system via a perceivedhigher risk route (such as via the Internet).

As a result of maintaining untrustworthy records for a set of files in afile system, the file system essentially contains two classes of files,namely trusted files (i.e., those files which lack an associateduntrustworthy record) and untrusted files (i.e., those files having anassociated untrustworthy record.

Performing Requested Actions on Untrusted Data

In step 1020 of FIG. 10, a policy is applied to determine how to processan action directed against untrusted data or requested by an untrustedentity. In an embodiment, step 1020 may be performed by cognitive assistmodule 236 applying a policy stored in policy data 239. However, otherembodiments may store policy data describing one or more policies fordetermine how to process an action directed against untrusted data inlocations other than VM0 230. Also, in other embodiments, one or moredifferent functional components, other than cognitive assist module 236,may determine how to process an action directed against untrusted dataor involving an untrusted requestor in step 1020.

In an embodiment, whenever an action is performed is requested to beperformed against untrusted data or involving an untrusted requestor,the request is communicated to cognitive assist module 236 so thatcognitive assist module 236 may apply a policy to determine whether therequest should be granted with full access, denied (which may beembodied as a permission error or an encryption error), or granted withlimited access. The policy may consider any number of factors, such asfactors concerning the identity of the entity requesting the performanceof the action, the manner in which the requesting entity gaining accessto the untrusted data, and/or the nature of the requested action.

As a result of applying the policy in step 1020, if the request toperform the action is not granted with full access or denied, then itmay be granted with limited access. One example of limited access whichmay be granted is that the requesting entity may be given read access toa portion, but not all, of the untrusted data. For example, therequesting entity may be given read access to only the header of a filebut not the complete file itself or may be given read access to aspecified number of bytes or blocks of the file.

Another example of granting the request with limited access is allowingthe requested action to be performed on the untrusted data, but theaction is performed within a different virtual machine from which therequest arose. The different virtual machine in which the action isperformed may be a pre-existing virtual machine (i.e., a virtual machinethat is already instantiated) or a virtual machine that will beinstantiated for purposes of performing the action.

To illustrate a concrete example with reference to FIG. 2, assume that arequest to perform open an untrusted text document was issued in LVM240. This request may be redirected to cognitive assist module 236. Therequest may be denied to be performed within LVM 240 by cognitive assistmodule 236, but cognitive assist module 236 may seamlessly migrate theperformance of the request to UCVM 266. Thus, the read operation on theuntrusted text document will fail in LVM 240, but will be performed inUCVM 266 in a manner transparent to the user. UCVM 266 may be configuredsuch that the request may be performed safely therein, e.g., UCVM 266may have no access to a network or to file system 242. From the user'sperspective, the user was able to do what the user wanted to do (i.e.,read the text document), but from a system perspective, the untrustedtext document was read in the proper virtual machine to protect theresources of the system.

Migrating the performance of an action directed against untrusted datato a virtual machine that is configured to contain any risk presented bythe untrusted data advantageously allows the user to use the untrusteddata without sacrificing the security of the computer system. Forexample, if an audio file, such as an “.MP3” file, is untrusted, thenthe user doesn't care which virtual machine plays the audio file, theuser just simply wants to listen to the audio file. By migrating theplaying of the untrusted audio file to a virtual machine having noexposure to system resources, the user may listen to the audio filewithout allowing any malicious code contained therein the opportunity toaffect any lasting change in the system.

Certain types of request may be considered as involving untrusted databy virtue of the type of request. Thus, certain types of requests, suchas a shell open command, may be considered as untrusted even if therequest does not specify any data. The rationale behind such a policy isthat certain types of requests can be used to cause mischief, andtherefore, should be performed in a manner to prevent unnecessaryexposure of system resources. To illustrate a concrete example withreference to FIG. 2, assume that a request to perform a shell opencommand was issued in VM0 230. This request may be redirected tocognitive assist module 236. The request may be denied, but seamlesslymigrated to UCVM 264 for processing. UCVM 264 may be configured suchthat the request may be performed safely therein, e.g., UCVM 264 mayhave no access to a network or to file system 242. Thus, the shell opencommand will fail in VM0 230 but will be performed in UCVM 264 in amanner transparent to the user. From the user's perspective, the userwas able to do what the user wanted to do, but from a systemperspective, the shell open command was performed in the proper virtualmachine to protect the resources of the system.

The policy itself used by cognitive assist module 236 in making thisdetermination may be relatively straightforward or arbitrarily complex.For example, the policy may be based, at least in part, upon metadatacontained within the untrustworthy records associated with the untrusteddata and may consider any number of factors.

In an embodiment, the policy applied in step 1020 may consider whetherthe entity requesting the performance of the action on the untrusteddata intends to interpret the untrusted data. In general, a certainlevel of limited scope of interpretation may not pose an unacceptablelevel of risk. For example, it may be permissible to allow certainapplications to read the header of untrusted file if the application isnot going to read the untrusted file in its entirety. Processes thatinterpret a file in its entirety present more of a security concern,while processes that consider a file as opaque data present less of aconcern. Thus, certain embodiments may, in performing step 1020, preventprocesses that interpret data from performing the requested action onuntrusted data, but allow processes that do not interpret data toperform the requested action on untrusted data.

One approach for determining whether an application or process will beinterpreting untrusted data is to examine the identity of the requestingapplication or process. Some applications or processes are known totreat files in an opaque manner, such as when a process that makes abackup of a file. Such applications or processes may be identified in awhite list comprised within policy data 239.

Also, certain mime-types may be deemed to be safe, such as a calendarfile. Such mime-types which pose little to no risk may also beidentified on a white list.

Alternately, some applications or processes are known to interpretfiles, e.g., an application responsible for rendering a text document ordigital image must interpret the file to render it properly.Applications or processes that are known to interpret data may beidentified in a black list comprised within policy data 239. In thisway, a white list or a black list may be consulted in step 1020 indetermining how to process the requested action. Thus, in a certainembodiments, a white list may be consulted in step 1020 to allow certainprograms/files to execute, while denying all others. Also, certain filesor programs may be flagged so that any action performed by or on themare performed in a separate virtual machine, such as a UCVM or LVM,having characteristics designed to address the security concerns posedthereby.

Another approach for determining whether an application or process willbe interpreting the untrusted data is to determine whether therequesting entity is a registered mime-type handler for the untrusteddata. If an application or process is the registered mime-type handlerfor the mime-type of a file, then it is very likely that the applicationor process will interpret the file. Conversely, if an application orprocess is not the registered mime-type handler for the mime-type of afile, then it is very likely that the application or process will notinterpret the file and treat the file as opaque data.

As an illustration of this principle, consider the application Outlook,a popular email application, available from Microsoft Corporation.Outlook is not the registered mime-type handler of the “.zip” mime-type.Therefore, if a user attempts to attach a compressed file having amime-type of “.zip” to an email in Outlook, the Outlook application willnot attempt to interpret the “.zip” file, but instead will treat thecompressed “.zip” file as a stream of bytes and simply attach thecompressed file to the email without interpreting the file. In thisexample, since Outlook will not be interpreting a compressed “.zip” fileby attaching it to an email, if a user instructs Outlook to do so, thenthe policy applied in step 1020 may permit such an action in recognitionthat the action poses an acceptable level of risk.

Certain mime-types are handled by the operating system itself, such asexecutable files. There is a concern in allowing such executable filesto execute unchecked given their potential to affect change andpotential carry malicious code. In an embodiment, if the user requeststhe execution of a file that is deemed untrustworthy, then the user maybe notified that the action, and by extension the file, isuntrustworthy. For example, a dialogue box may be displayed to the userindicated that the file the user just clicked on is an untrusted file.Alternatively, information about a file being untrusted may be displayedprior to the user clicking on the file to initiate execution of thefile, such as by displaying such information to the user when the userdoes a move over operation over the icon for the file or right clicks onthe icon for the file.

The user may be presented with an option to execute the file in anuntrusted manner. If the user selects the option to execute theuntrusted file, the untrusted file may be executed within a particularvirtual machine, such as a UCVM, specifically tailored to prevent tocontain the untrusted file. For example, the UCVM in which the untrustedfile executed may not have any exposure to a network or a file system.For the same reason, the UCVM in which the untrusted file is executedmay only exist during the execution of the file. When the file is doneexecuting, the UCVM may be de-instantiated. As the UCVM exists only aslong as necessary to run the program, no data need be persisted as aresult of executing the file. On the other hand, if persisting changesmade by an executable file is desirable by an IT administrator, this maybe accomplished by determining the changes made to UCVM as a result ofthe execution of the program and subsequently storing those changes sothe changes may be injected into another virtual machine at a laterdate.

In an embodiment, the policy applied in step 1020 may consider how therequesting entity accessed the file. Files may be access from differentAPI levels. Such differing API levels include, in decreasing proximityto the user, an Explorer Shell Interface API level, a Win32 API level,and a Kernel API level. In other words, a user is more likely toinitiate an action that utilizes the Explorer Shell Interface API level.The Explorer Shell Interface API may in turn make calls into the Win32API level, and so on. Thus, an action initiated by the user is morelikely to access a file via the Explorer Shell Interface API than theKernel API, whereas a malicious executable file is more likely toutilize the Win32 API to discover and interact with files rather thanthe Explorer Shell Interface API.

In an embodiment, an action initiated by a user is, when at allpossible, attempted to be performed to provide the user with a userexperience that behaves as expected and is close to native as possible.However, an action that is not initiated by a user is not afforded thesame deference because such an action is more likely to be the result ofmalicious code that has been inadvertently introduced into the computersystem.

To illustrate an example, imagine a malicious program that traverses allthe files in a file system on the client, reads the files, and extractstext from them. To prevent this hypothetical malicious program and othersuch programs from succeeding, embodiments of the invention preventssuch programs operating without benefit of either (a) being initiated bythe user or (b) being identified on a white list from discovering thepresence of files in the computer system. In this way, this hypotheticalmalicious program would be prevented from learning about any filesstored on the disk.

Similarly, certain embodiments, in performing step 1020, may deny theexistence of a file to a program if the program is accessing the filethrough an API level that raises some concern. For example, at the filesystem level, embodiments may prevent certain kinds of access that arenot the intended use case, such as an action against a file that doesnot originate from the Explorer Shell Interface API. Such an approachwould prevent an indexing or backup program from stumbling across a filefor mischievous purposes. As a result, in an embodiment, if the actionrequested to be performed in step 1020 is not user initiated or isaccessed from a API layer that is prohibited, then the action is deemeduntrustworthy and the entity requesting the performance of the action onthe file is informed the file does not exist (even if the file doesexist).

Note that the policy consulted in step 1020 may be, but need not be, thesame policy which was consulted in step 1010. In other words, anembodiment may store (a) a first set of policy data that describes oneor more policies for identifying untrusted data or an untrusted actionand (b) a second set of policy data that describes how to process anaction involving untrusted data or an untrusted action.

In an embodiment, all files, or any portion thereof, in a file systemthat are deemed untrustworthy may be stored in an encrypted fashion.Thus, any program that attempts to open an untrusted file (for example,by scanning the file system) would be unable to read the untrusted file,thereby rendering the program safe from any malicious code containedwithin the untrusted file.

Embodiments of the invention may provide mechanisms to safely performany operation against an untrusted file (such as opening or editing thefile) by only permitting the operation to occur within a virtualmachine, such as a UCVM. The encryption key(s) to encrypt and decryptuntrusted files may be managed using a variety of different approaches.To illustrate, such key(s) may be implemented as an enterprise wide PKIsystem for untrusted files (or classes of untrusted files) in anorganization or such key(s) may be system local only. Any of the filesdeemed to be untrustworthy may be prevented from being decrypted unlessthe files are decrypted within a virtual machine instantiated for thatpurpose.

Certain embodiments may also make the un-encrypted data of a particularfile type available to certain programs which are known to not interpretthe contents of the particular file type. For example, embodiments mayallow an email client, such as Microsoft Outlook, to read a rawuntrusted file (decrypted) in response to a user directed “attach file”operation while composing an email. This operation may be permitted byan embodiment because Microsoft Outlook is not registered as a MIMEhandler for the file type in questions, and will never try to interpretthe contents of the file being attached, but would simply blindlycommunicate the attached file further to the mail server.

Creating a Distinct Name Space Entity

In an embodiment, in the performance of step 1020, if cognitive assistmodule 236 permits an action to be performed on the file, cognitiveassist module 236 may create (if not already created) a separate anddistinct name space entity for the file so that the names space entityfor file is separate from the file itself. The name space entity may beembodied as a link file that references the original file. The purposeof creating the separate name space entity for the file is so that whenthe original file is detected by a program, the program still does nothave access to the file without traversing the link provided by the namespace entity.

The name space entities described above serve as proxies for theoriginal files while preserving the user's ability to interact with thereal untrusted files (the real untrusted files may be managed byembodiments of the invention). The proxy name space entities appearvisually just as the original real untrusted files would have appeared,with the same icons and similar set of supported user operations. Forexample, performing a right click mouse operation on a proxy file maycause the display of the same menu as performing the same operation onthe real untrusted file represented by the proxy file.

Ensuring User Experience as Close to Native as Possible

Certain embodiments support a graphical user interface that looks andbehaves as close as possible to the graphical user interface provided byoperating system 232. For example, all icons of files rendered ondisplay 912 may look like the typical icon for that file type. Further,when a user double-clicks on an icon, the resulting action should be thesame as expected, e.g., an application should be launched or a filedisplayed.

Embodiments may be designed to implement a comparable view from theshell. For example, if a user opens a file using the ninth associatedmime-handler, then a compatible view from the shell should still besupported.

Untrusted files may be rendered by embodiments to appear as native filesor trusted files to users so users may perform normal file operations onuntrusted files without compromising security. Such normal fileoperations include, without limitation, rename operations, deleteoperations, copy operations, drag-and-drop operations, and attributechange operations. Security need not be compromised because such normalfile operations may be performed on an untrusted file in a VM, such as aUCVM, in a manner transparently to the user.

Processing Requested Actions on Secret Data

In certain embodiments, data may be associated with a record(hereinafter a “secret record”) to label the data as secret data. Forexample, certain sensitive corporate data, such as a set of files, mayeach be labeled with a secret record. The purpose of the secret recordis to inform cognitive assist module 236 that any operation performed onthe file should confirm to policies identified in policy data 239. Inthis way, a corporation may define policies that restrict what actionsmay be performed on their secret data. For example, a file that isassociated with a secret record may be prevented by cognitive assistmodule 236 from being printed, attached to an email, or otherwisecommunicated outside of client 200.

Hardware Mechanisms

In an embodiment, client 200 of FIG. 2 may be implemented on, include,or correspond to a computer system. FIG. 9 is a block diagram thatillustrates a computer system 900 upon which an embodiment of theinvention may be implemented. In an embodiment, computer system 900includes processor 904, main memory 906, ROM 908, storage device 910,and communication interface 918. Computer system 900 includes at leastone processor 904 for processing information. Computer system 900 alsoincludes a main memory 906, such as a random access memory (RAM) orother dynamic storage device, for storing information and instructionsto be executed by processor 904. Main memory 906 also may be used forstoring temporary variables or other intermediate information duringexecution of instructions to be executed by processor 904. Computersystem 900 further includes a read only memory (ROM) 908 or other staticstorage device for storing static information and instructions forprocessor 904. A storage device 910, such as a magnetic disk or opticaldisk, is provided for storing information and instructions.

Computer system 900 may be coupled to a display 912, such as a cathoderay tube (CRT), a LCD monitor, a television set, and the like, fordisplaying information to a user. In an embodiment, display 912 mayinclude a virtual display that is being rendered on a physical display.The virtual display may be rendered using a variety of protocols, suchas a remote desktop protocol (RDP). An input device 914, includingalphanumeric and other keys, is coupled to computer system 900 forcommunicating information and command selections to processor 904. Othernon-limiting, illustrative examples of input device 914 include a mouse,a trackball, or cursor direction keys for communicating directioninformation and command selections to processor 904 and for controllingcursor movement on display 912. While only one input device 914 isdepicted in FIG. 9, embodiments of the invention may include any numberof input devices 914 coupled to computer system 900.

Embodiments of the invention are related to the use of computer system900 for implementing the techniques described herein. According to oneembodiment of the invention, those techniques are performed by computersystem 900 in response to processor 904 executing one or more sequencesof one or more instructions contained in main memory 906. Suchinstructions may be read into main memory 906 from anothermachine-readable medium, such as storage device 910. Execution of thesequences of instructions contained in main memory 906 causes processor904 to perform the process steps described herein. In alternativeembodiments, hard-wired circuitry may be used in place of or incombination with software instructions to implement embodiments of theinvention. Thus, embodiments of the invention are not limited to anyspecific combination of hardware circuitry and software.

The term “machine-readable storage medium” as used herein refers to anytangible medium that participates in storing instructions which may beprovided to processor 904 for execution. Such a medium may take manyforms, including but not limited to, non-volatile media and volatilemedia. Non-volatile media includes, for example, optical or magneticdisks, such as storage device 910. Volatile media includes dynamicmemory, such as main memory 906.

Non-limiting, illustrative examples of machine-readable media include,for example, a floppy disk, a flexible disk, hard disk, magnetic tape,or any other magnetic medium, a CD-ROM, any other optical medium, a RAM,a PROM, and EPROM, a FLASH-EPROM, any other memory chip or cartridge, orany other medium from which a computer can read.

Various forms of machine readable media may be involved in carrying oneor more sequences of one or more instructions to processor 904 forexecution. For example, the instructions may initially be carried on amagnetic disk of a remote computer. The remote computer can load theinstructions into its dynamic memory and send the instructions over anetwork link 920 to computer system 900.

Communication interface 918 provides a two-way data communicationcoupling to a network link 920 that is connected to a local network. Forexample, communication interface 918 may be an integrated servicesdigital network (ISDN) card or a modem to provide a data communicationconnection to a corresponding type of telephone line. As anotherexample, communication interface 918 may be a local area network (LAN)card to provide a data communication connection to a compatible LAN.Wireless links may also be implemented. In any such implementation,communication interface 918 sends and receives electrical,electromagnetic or optical signals that carry digital data streamsrepresenting various types of information.

Network link 920 typically provides data communication through one ormore networks to other data devices. For example, network link 920 mayprovide a connection through a local network to a host computer or todata equipment operated by an Internet Service Provider (ISP).

Computer system 900 can send messages and receive data, includingprogram code, through the network(s), network link 920 and communicationinterface 918. For example, a server might transmit a requested code foran application program through the Internet, a local ISP, a localnetwork, subsequently to communication interface 918. The received codemay be executed by processor 904 as it is received, and/or stored instorage device 910, or other non-volatile storage for later execution.

In the foregoing specification, embodiments of the invention have beendescribed with reference to numerous specific details that may vary fromimplementation to implementation. Thus, the sole and exclusive indicatorof what is the invention, and is intended by the applicants to be theinvention, is the set of claims that issue from this application, in thespecific form in which such claims issue, including any subsequentcorrection. Any definitions expressly set forth herein for termscontained in such claims shall govern the meaning of such terms as usedin the claims. Hence, no limitation, element, property, feature,advantage or attribute that is not expressly recited in a claim shouldlimit the scope of such claim in any way. The specification and drawingsare, accordingly, to be regarded in an illustrative rather than arestrictive sense.

What is claimed is:
 1. One or more non-transitory computer-readablestorage mediums storing one or more sequences of instructions formanaging potentially malicious files using virtual machines, which whenexecuted by one or more processors, cause: in response to receiving arequest to perform an action on a file, a client applying a policy todetermine whether the action is deemed trustworthy; and the clientinstantiating, without human intervention and based on the policy, avirtual machine in which the action is to be performed against the file,wherein the policy determines which hardware resources of the client andwhich software resources of the client, other than said file, areaccessible to the virtual machine.
 2. The one or more non-transitorycomputer-readable storage mediums of claim 1, wherein execution of theone or more sequences of instructions further cause: upon determiningthat the action is deemed untrustworthy, performing a responsive action,wherein the responsive action includes one or more of: disallowingaccess to the file, adding an entry describing characteristics of theuntrustworthy action to an audit log to facilitate future analysis, andissuing an alert to an authority to request permission to access thefile.
 3. The one or more non-transitory computer-readable storagemediums of claim 1, wherein the policy indicates that if the fileoriginates from an untrusted domain, then the action is deemeduntrustworthy.
 4. The one or more non-transitory computer-readablestorage mediums of claim 1, wherein the policy indicates that if theaction is to be performed by a mime-type handler associated with thefile, then the action is deemed untrustworthy.
 5. The one or morenon-transitory computer-readable storage mediums of claim 1, wherein thepolicy indicates that if the action involves a process that previouslyinterpreted an untrustworthy file, then the action is deemeduntrustworthy.
 6. The one or more non-transitory computer-readablestorage mediums of claim 1, wherein the policy indicates that if theaction involves an entirety of the file being interpreted, then theaction is deemed untrustworthy.
 7. The one or more non-transitorycomputer-readable storage mediums of claim 1, wherein execution of theone or more sequences of instructions further causes: upon determiningthat the action is deemed untrustworthy, storing data indicating thatthe file is untrustworthy.
 8. The one or more non-transitorycomputer-readable storage mediums of claim 1, wherein execution of theone or more sequences of instructions further causes: detecting, withouthuman intervention, an attempt to interpret the contents of the file. 9.The one or more non-transitory computer-readable storage mediums ofclaim 1, wherein the policy indicates that if the action involves aportion of the file being interpreted, then the action is deemedtrustworthy.
 10. The one or more non-transitory computer-readablestorage mediums of claim 9, wherein the portion is a header of the file,a specified portion of the total number of bytes of the file, or aspecified portion of the total number of blocks of the file.
 11. The oneor more non-transitory computer-readable storage mediums of claim 1,wherein said virtual machine is a first virtual machine, wherein theaction originated in a second virtual machine, and wherein the policyspecifies that the action is to be performed in a different virtualmachine other than said second virtual machine.
 12. The one or morenon-transitory computer-readable storage mediums of claim 11, wherein auser is informed by the client that the action is performed but notinformed by the client that the action is performed in the differentvirtual machine.
 13. The one or more non-transitory computer-readablestorage mediums of claim 1, wherein execution of the one or moresequences of instructions further causes: upon determining that theaction is deemed untrustworthy, storing data indicating that a processassociated with the action is untrustworthy.
 14. The one or morenon-transitory computer-readable storage mediums of claim 1, wherein thepolicy indicates that if the action involves a process that hascommunicated with untrusted data or an untrusted network over theInternet, then the action is deemed untrustworthy.
 15. The one or morenon-transitory computer-readable storage mediums of claim 1, wherein thepolicy indicates that if the file is located in a particular location,then the file or action is deemed untrustworthy.
 16. The one or morenon-transitory computer-readable storage mediums of claim 1, wherein thepolicy specifies that actions initiated by a user are deemedtrustworthy, and wherein the policy specifies that actions notassociated with user-initiated action are deemed untrustworthy.
 17. Theone or more non-transitory computer-readable storage mediums of claim 1,wherein the policy specifies that if the file is created by a process ina set of identified processes, then the action is deemed untrustworthy.18. The one or more non-transitory computer-readable storage mediums ofclaim 1, wherein the policy specifies that if the file is created by aprocess in a set of identified processes, then the action is deemedtrustworthy.
 19. The one or more non-transitory computer-readablestorage mediums of claim 1, wherein the policy specifies a preferred APIlevel to interact with the file, and wherein if the action arises fromany API level other than the preferred API level, then the action isdeemed untrustworthy.
 20. The one or more non-transitorycomputer-readable storage mediums of claim 19, wherein the preferred APIlevel is one of a number of API levels comprising an Explorer ShellInterface API level, a Win32 API level API, and a Kernel API level. 21.The one or more non-transitory computer-readable storage mediums ofclaim 1, wherein execution of the one or more sequences of instructionsfurther causes: providing notification, to a user, that the action isdeemed untrustworthy; and in response to receiving user input whichindicates that the untrustworthy action is to be performed in the samevirtual machine in which the action arose, performing said actionagainst said file in said virtual machine.
 22. The one or morenon-transitory computer-readable storage mediums of claim 1, whereinexecution of the one or more sequences of instructions further causes:the client denying the performance of the action upon determining thatthe policy indicates that the file is a member of a protected set offiles and the action is a member of a prohibited set of actions.
 23. Theone or more non-transitory computer-readable storage mediums of claim 1,wherein said policy is a first policy, and wherein execution of the oneor more sequences of instructions further causes: in response todetermining that the file or action is deemed untrustworthy using asecond policy, consulting a third policy to identify a responsive actionto perform.
 24. The one or more non-transitory computer-readable storagemediums of claim 1, wherein the instantiation of the virtual machinedoes not require booting of the virtual machine.
 25. The one or morenon-transitory computer-readable storage mediums of claim 1, whereineach file in said set of files deemed untrustworthy is opened in aseparate virtual machine by said client based on said policy.
 26. One ormore non-transitory computer-readable storage mediums storing one ormore sequences of instructions for managing potentially malicious filesusing virtual machines, which when executed by one or more processors,cause: in response to receiving a request to perform an action on afile, a client applying a policy to determine whether the action isdeemed trustworthy; the client instantiating, without human interventionand based on the policy, a virtual machine in which the action is to beperformed against the file, wherein the policy determines whichresources of the client are accessible to the virtual machine; creatinga name space entity for the file that is separate from the file; and inresponse to receiving an access request for the file through aparticular API level, processing the access request by providing thename space entity to the requestor rather than the file.
 27. One or morenon-transitory computer-readable storage mediums storing one or moresequences of instructions for managing potentially malicious files usingvirtual machines, which when executed by one or more processors, cause:in response to receiving a request to perform an action on a file, aclient applying a policy to determine whether the action is deemedtrustworthy; the client instantiating, without human intervention andbased on the policy, a virtual machine in which the action is to beperformed against the file, wherein the policy determines whichresources of the client are accessible to the virtual machine, whereinsaid file is in a set of files deemed untrustworthy; encrypting said setof files deemed to be untrustworthy; and preventing any of the set offiles deemed to be untrustworthy from being decrypted unless the set offiles are decrypted within said virtual machine instantiated for thatpurpose.
 28. The one or more non-transitory computer-readable storagemediums of claim 1, wherein the resources of the client that areaccessible to the virtual machine are those resources necessary to viewor edit the file.
 29. A client, comprising: one or more processors; oneor more non-transitory storage mediums storing one or more sequences ofinstructions for managing potentially malicious files using virtualmachines, which when executed by the one or more processors, causes: inresponse to receiving a request to perform an action on a file, a clientapplying a policy to determine whether the action is deemed trustworthy;and the client instantiating, without human intervention and based onthe policy, a virtual machine in which the action is to be performedagainst the file, wherein the policy determines which hardware resourcesof the client and which software resources of the client, other thansaid file, are accessible to the virtual machine.
 30. A method formanaging potentially malicious files using virtual machines, comprising:in response to receiving a request to perform an action on a file, aclient applying a policy to determine whether the action is deemedtrustworthy; and the client instantiating, without human interventionand based on the policy, a virtual machine in which the action is to beperformed against the file, wherein the policy determines which hardwareresources of the client and which software resources of the client,other than said file, are accessible to the virtual machine.